1 



HEATING AND VENTILATION 



"Ms QraW'JlillBook (n. 7ne. 

PUBLISHERS OF BOOKS F O R^ 

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rr fTM rn mni 



HEATING 



AND 



VENTILATION 



BY 
JOHN E. ALLEN 

DEAN OF THE DEPARTMENT OP ENGINEERING AND ARCHITECTURE 

UNIVERSITY OF MINNESOTA; MEMBER AMERICAN SOCIETY 

OF HEATING AND VENTILATING ENGINEERS; MEMBER 

AMERICAN SOCIETY OF MECHANICAL ENGINEERS 

AND 



J. H. WALKER 



SUPERINTENDENT OF CENTRAL HEATING, THE DETROIT EDISON 

COMPANY ; MEMBER AMERICAN SOCIETY OF HEATING 

AND VENTILATING ENGINEERS 



First Edition 



McGRAW-HILL BOOK COMPANY, Inc. 

239 WEST 39TH STREET. NEW YORK 



LONDON: HILL PUBLISHING CO., Ltd. 

6^8 BOUVERIE ST., E. C, 

1918 



K 



i 



Copyright, 1918, by the 
McGraw-Hill Book Company, Inc. 



d^ 



.JIJN 12 1918 



^ 



^ 



THE MAPLK I'RESS VORKL PA 




r/ ©CI.A499317 



1 



PREFACE 

This book is offered as a text-book upon the subject of heating 
and ventilation for use in the engineering and architectural 
schools. It is also believed that the development of working 
methods of design and the including of the various tables and 
charts make the book of some value as a handbook for the 
practicing engineer and architect. 

Calculus has been employed to some extent in the develop- 
ment of certain expressions, this having been deemed desirable 
for the sake of completeness. For architectural students and 
others not equipped with higher mathematics, such parts may 
be omitted, however, without destroying the structure of the 
book. Problems have been included at the end of many of the 
chapters in order to illustrate the principles involved, but it is 
felt that they can be profitably supplemented by the actual 
designing by the student of complete heating and ventilating 
systems for representative buildings of various types. 

Acknowledgment is made to the American Blower Company 
and the Buffalo Forge Company for the use of various charts 
and tables. 

Information as to the typographical errors which are doubtless 
present in this initial edition will be gratefully received. 

J. R. A. 

March, 1918. J. H. W. 



CONTENTS 

Page 

Preface v 

CHAPTER I 

Heat 

Measurement of Heat 1 

Measurement of Temperature 2 

Unit of Heat 4 

CHAPTER II 

Heat Losses from Buildings 

Radiation 9 

Conduction 10 

Convection 11 

Loss of Heat from Buildings 12 

Heat Lost Due to Infiltration 18 

Calculation of Heat Loss 20 

Approximate Rules 21 

CHAPTER III 

Different Methods of Heating 

Grates 25 

Stoves 26 

Hot-air Furnaces 26 

Direct Steam Heating 27 

Direct Heating by Hot Water 28 

Indirect Heating 29 

Economy of Heating Systems 31 

CHAPTER IV 

Properties of Steam 

The Formation of Steam 33 

Properties of Steam 34 

Steam Tables 36 

Mechanical Fixtures 37 

vii 



viii CONTENTS 

CHAPTER V 

Radiators 

Page 

Direct Cast-iron Radiators 45 

Pressed Metal Radiators 50 

Heat Transmission from Radiators 51 

Location of Radiators 56 

Proportioning Radiation 57 

Indirect Radiators 60 

CHAPTER VI 

Steam Boilers 

Fuel 69 

Combustion 71 

Smoke 72 

Types of Boilers 74 

The Downdraft Boiler 77 

Boiler Rating 81 

Draft and' Chimney Construction 83 

CHAPTER VII 

Steam Heating Systems 

Single-pipe Systems 87 

Two-pipe Systems 89 

Overhead System 91 

Vapor System 93 

Vacuum Return Line System 99 

CHAPTER VIII 

Pipe, Fittings, Valves, and Accessories 

Pipe 102 

Fittings 104 

Valves 106 

Pipe Covering 109 

Air-valves Ill 

Traps 112 

Reducing Valves 115 

CHAPTER IX 

Steam Piping 

Principles Involved in Piping Design 119 

Expansion 119 



i 

J 



CONTENTS ix 

Page 

Drainage 120 

Mains and Branches 121 

Risers 122 

Pipe Hangers 124 

Radiator Connections 128 

Flow of Steam in Pipes 131 

Selection of Pipe Sizes 134 

CHAPTER X 

Hot-water Systems 

Theory of Flow in a Gravity System 142 

Types of Gravity Systems 146 

Method of Computing Pipe Sizes 151 

Forced Circulation 158 

Pumpage, Friction, and Temperature Drop 159 

Calculation of Pipe Sizes 161 

CHAPTER XI 

Automatic Temperature Control 

Manual Control 163 

Automatic Control Applied to Boiler 164 

Automatic Control of Radiators 166 

Advantages of Automatic Control 167 

CHAPTER XII 

Air and Its Properties 

Composition of Air 169 

Water Vapor ] 70 

Measurement of Humidity 173 

Psychrometric Chart 175 

CHAPTER XIII 

Ventilation 

Ventilation Standards 179 

Amount of Air Required • 181 

Methods of Measuring Air Supply 182 

Temperature and Humidity 184 

Air Movement 187 

Odors 187 

Dust and Bacteria 188 



X CONTENTS 

CHAPTER XIV 
Hot-air Furnace Heating 

Page 

Furnaces 192 

Cold-air Pipe 196 

Hot-air Pipes .' 197 

Test of a Hot-air Furnace 204 

CHAPTER XV 

Design of Fan Systems 

General Arrangement 207 

Calculation of Air Quantities 208 

Flow of Air in Ducts 209 

Proportioning Duct Systems 218 

Theory of the Centrifugal Fan 223 

Fan Performance 226 

Selection of a Fan ■ 228 

Heaters 233 

Transmission of Heat from Fan Coils 236 

CHAPTER XVI 

Air-washers and Air Conditioning 

The Air-washer 244 

Air Conditioning 246 

Humidity Control 248 

Cooling and De-humidification 249 

CHAPTER XVII 

Fan Systems for Various Types of Buildings 

Heating of PubUc Buildings 252 

Factory Heating 253 

Heating of Theatres and Auditoriums 255 

Estimating Heating Requirements 255 

CHAPTER XVIII 

Central Heating 

Location of Power Plant 258 

Systems of Distribution 260 

Methods of Carrying Pipes 262 

Expansion Fittings 265 

Tunnels 266 

Index 301 



HEATING AND VENTILATION 

CHAPTER I 
HEAT 

1. Heat. — Heat has long been known to be a form of energy. 
Modern theories as to the exact nature of heat conceive it to be a 
motion or agitation of the molecules, or extremely small particles, 
of which every body is composed. The intensity of the heat in 
a body is believed to be dependent upon the violence of this 
molecular disturbance. Every substance on the earth contains 
some heat and to say that a body is ^'cold, " means simply that 
it contains a relatively small amount of molecular motion. 

Heat and many other forms of energy are mutually convertible. 
For example, heat energy is converted into electrical energy in a 
generating plant and electric energy is re-converted into heat 
energy in an electric stove. Heat energy is converted into 
mechanical energy in a steam locomotive and some of this 
mechanical energy is re-converted into heat energy by the fric- 
of the locomotive brakes. 

2. Measurement of Heat. — In measuring heat there are two 
quantities to be considered : the intensity of heat and the amount 
of heat. A small piece of white-hot metal may not contain as 
great a quantity of heat as a pail of warm water, but the intensity 
of the heat in the former is much greater. The intensity of 
heat is expressed by the word temperature. The temperature 
of a body is most easily measured by noting its effect upon some 
other substance. 

One measure of the intensity of heat in a body is its ability to 
transmit heat to a body of lower temperature. Heat will flow 
from a body of higher temperature to one of lower temperature 
hut will never flow, of itself, from one body into another of higher 
temperature. When two bodies of different temperatures are 
placed in thermal contact a heat exchange takes place until the 
two bodies are at the same temperature and thermal equilibrium 

1 



2 HEATING AND VENTILATION 

is reached. We may, therefore, state that two bodies are at the 
same temperature when there is no tendency for heat to flow 
from the one to the other. 

3. Measurement of Temperature. — The measurement of 
temperature is usually based upon some arbitrary scale which 
is standardized by comparison with some well-established phys- 
ical ''fixed points." In mechanical engineering most measure- 
ments of temperature are made on the Fahrenheit scale. On 
this scale the freezing point of water is taken at 32° and the 
boiling point at sea level barometer at 212,° the tube of the 
thermometer between these points being divided into 180 equal 
parts or degrees. There is, however, an increasing use of the 
Centigrade scale among engineers. In the Centigrade scale 
the distance between the freezing point and the boiling point is 
divided into 100 equal parts. The freezing point on the scale 
is marked and the boiling point is marked 100°. Both the 
Fahrenheit and the Centigrade scales assume an arbitrary point 
for the zero of the scale. 

If the temperature Fahrenheit is denoted by t/ and the tempera- 
ture Centigrade by ic, then the conversion from one scale to the 
other may be made by the following equations: 

tf = ~tc + S2 

t. = ^{tf- 32) 

The most common instrument for measuring temperature is 
the mercury thermometer. Mercury like most other substances 
undergoes an increase in volume when heated, and is particularly 
useful because the amount of its expansion for equal increments 
in temperature is nearly constant over a wide range in tempera- 
ture. The thermometer is a glass tube of very fine bore with a 
bulb blown on one end and filled with mercury, as shown in 
Fig. 1. The air is expelled from the tube by boiling the mercury 
and the tube is sealed. The space above the mercury then 
contains mercury vapor at a very low pressure. The 32° and the 
212° points of the Fahrenheit scale are located on the tube or 
stem by immersing the bulb in a freezing mixture and in boiUng 
water. The distance between these points is then divided into 
180 equal parts. 



HEAT 3 

To do accurate work with the thermometer is much more 
difficult than is generally supposed. The mercury of the ordinary 
glass thermometer does not expand in exactly equal amounts for 
equal increments of temperature and the bore of the thermometer 
is never absolutely uniform throughout the length of the tube. 
All of these irregularities produce errors in observation. When 
measuring the temperature of liquids the depth to which ^ 
the thermometer is immersed affects the reading and 
the thermometer should be calibrated at the depth at 
which it is to be used. 

It is really its own temperature that the thermometer 
indicates and the accuracy with which the temperature 
of a substance is measured depends upon the complete- 
ness with which its temperature is reached by the ther- 
mometer. The thermometer must therefore be brought 
into intimate thermal contact with the substance to be 
measured. In measuring the temperature of fluids in 
pipes, a brass or steel well is inserted into the pipe and 
filled with some liquid such as oil or mercury, in which 
the thermometer is immersed. If the thermometer is 
used to measure the temperature of the air in the room 
in which there are objects of a higher temperature than 
the thermometer, its bulb must be protected from the 
radiant heat of these hot bodies; otherwise the ther- 
mometer will not read the temperature of the air sur- 
rounding it but will be affected by the radiant heat 
absorbed by it. When accurate temperature measure- 
ments are desired a careful study should be made of 
the thermometer and its errors and all inaccuracies 
should be allowed for by careful calibration. 

The mercury thermometer can be used up to tempera- 
tures of 500°F. and for temperatures as low as —40°. 
Where lower, temperatures must be measured it is cus- 
tomary to use thermometers filled with alcohol, and for 
temperatures higher than 500°F. some form of pyro- 
meter must be used. High temperatures may be deter- 
mined approximately by color. For each temperature 
there is a corresponding color and an approximation to 
the actual temperature can be made by an observation of the 
color of the heated substance. Table I gives the temperature 
colors. 



A 



HEATING AND VENTILATION 
Table I. — Temperature Colors 



Color 



Temp. C. 



Temp. F. 



Faint red 

Dark red 

Faint cherry . . . 

Cherry 

Bright cherry . . 
Dark orange . . . 
Bright orange . 

White heat 

Bright white . . 
DazzUng white 



525 

700 

800 

900 
1,000 
1,100 
1,200 
1,300 
1,400 
1,500-1,600 



977 
1,292 
1,472 
1,652 
1,832 
2,012 
2,192 
2,372 
2,552 
2,732-2,912 



4. Absolute Temperature. — In any theoretical consideration 
of heat it is necessary to have some absolute scale of temperature. 
The point at which the molecules of a substance would have no 
motion is considered to be the absolute zero point. According 
to Marks and Davis this point is theoretically at 491.64° below 
the freezing point of water on the Fahrenheit scale, or 459.64° 
below the Fahrenheit zero. On the Centigrade scale the absolute 
zero is at —273.1°. To convert any temperature on the Fahren- 
heit or Centigrade scale to absolute temperature the following 
formulae are used: 



Tf = tf-\- 460 (approximately) 
Tc = tc -{- 273 (approximately) 



in which the absolute temperatures on the Fahrenheit and Cen- 
tigrade scales are represented by Tf and Tc. These expressions 
are sufficiently accurate for ordinary work. 

No one has as yet been able to produce a temperature as low 
as the absolute zero. The lowest temperatures ever attained 
have been produced in the heat laboratory at Leyden, Holland, 
at which there has been produced a temperature of 489° below 
the Fahrenheit freezing point. 

5. Unit of Heat. — Heat must be measured by the effect which 
it produces upon some substance. The unit of heat used in 
mechanical engineering is the heat required to raise the tempera- 
ture of a pound of water one degree Fahrenheit. This is called 
the British thermal unit and is denoted by B.t.u. As this quantity 



II 



HEAT 5 

is not exactly the same at all temperatures it is necessary to 
specify further a definite temperature at which the unit is to be 
established. The practice of different authorities varies in this 
regard, but the mean B.t.u. established by Marks and Davis is 
becoming generally used. This is defined as the one hundred 
and eightieth part of the heat necessary to raise the temperature 
of one pound of water from 32° to 212°r. 

6. Specific Heat. — Specific heat may be defined as the heat 
necessary to raise the temperature of a unit weight of a sub- 
stance through one degree. It represents the specific thermal 
capacity of a body. In English units the specific heat is the 
quantity of heat necessary to raise a pound of a substance one 
degree Fahrenheit, expressed in British thermal units. Since 
the British thermal unit is the quantity of heat necessary to 
raise a pound of water one degree Fahrenheit, we may say that 
the specific heat represents the ratio between the heat necessary 
to raise a unit weight of a body one degree and the heat neces- 
sary to raise the same weight of water one degree. 

When a substance is heated at constant pressure its volume 
increases against that pressure and external work is done as a 
consequence. The external work may be computed by multiply- 
ing the pressure by the change in volume. When heated at 
constant volume no external work is done as no movement is made 
against an external resistance. In any substance, such as a gas, 
which has a large coefficient of expansion due to heat, it is 
therefore necessary to distinguish between the two specific heats, 
the specific heat of constant pressure and the specific heat of con- 
stant volume. The difference between the two specific heats in any 
particular gas must be equal to the heat equivalent of the external 
work done when a unit weight of the gas is raised one degree at a 
constant pressure. 

The quantity of heat added to or removed from a body is 
equal to 

WC(t2 - h) 
in which 

W = weight of the body in pounds. 

C = specific heat of the material. 

ti = lower temperature Fahrenheit. 

^2 = higher temperature Fahrenheit. 



HEATING AND VENTILATION 

Table II. — Specific Heats 

Substance Specific 

heat 

Liquids: 

Water 1 .0000 

Alcohol 0.6220 

Turpentine . 4720 

Petroleum . 4340 

Olive oil 0.3090 

Metals: 

Cast iron . 1298 

Wrought iron . 1138 

Soft steel 0.1165 

Copper 0.0951 

Brass 0.0939 

Tin. 0.0569 

Lead 0.0314 

Aluminum . 2185 

Zinc 0.0953 

Minerals : 

Coal 0.2777 

Marble 0.2159 

Chalk 0.2149 

Stones generally . 2100 

Limestone . 2170 

Building Materials: 

Brickwork . 1950 

Masonry . 2000 

Plaster . 2000 

Pine wood 0.4670 

Oak wood 0.5700 

Birch 0.4800 

Glass 0. 1977 



Specific Heat of Gases 

Constant Constant 

Substance pressure volume 

Air 0.2415 0. 1729 

Oxygen 0.2175 0. 1550 

Hydrogen 3.4090 2.4122 

Nitrogen 0.2438 0. 1727 

Steam 0.5000 0.3500 

Carbonic acid, CO2 0.2479 0.1758 

Ammonia 0.5080 0.2990 

Example. — It is required to raise the temperature of a cast-iron radiator f 

weighing 300 pounds from 70° to 212°. The temperature through which • 

the iron would be raised would then be 212° minus 70° or 142°. From Table ' 



HEAT 7 

II we see that to raise 1 pound of cast iron 1° would require 0.1298 heat 
units. To raise 1 pound 142° would require 142 times 0.1298 or 18.43 heat 
units, and to raise 300 pounds 1° would require 300 times this amount or 
5529 B.t.u., the heat required to heat the radiator. 

Example. — A church 80 by 100 feet inside has stone walls 2^ feet thick 
for 10 feet above the ground and for the remaining 20 feet 2 feet thick. The 
roof has a ^ pitch and is made of 2 by 8-inch rafters, 16 inches on centers, 
covered with 1 inch of pine boarding, tar paper and slate ^ inch thick. 
Main floor composed of two 1-inch thicknesses of boards laid on 2 by 12- 
inch joists, 16-inch centers. Ceiling is of plaster ^i inch thick. The church 
has 20 windows, 6 feet wide and 15 feet high, 12 windows 4 feet wide and 
6 feet high, and 2 doors, 8 feet wide and 12 feet high. Allowing an addition 
of 15 per cent, for furnishings, find the heat required to raise the tempera- 
ture of the structure from 0° to 50°. 

Weight of stonework, stone weighing 160 pounds per cubic foot: 

370 X 10 X 23^ = 9,250 cubic feet 

368 X 20 X 2 = 14,720 cubic feet 

84-^2X40X2X2 = 6,720 cubic feet 



30,690 cubic feet 



Deduction for windows and doors : 

20 X 6 X 15 X 2 = 3,600 

12 X 4 X 6 X 2 = 576 

2 X 8 X 12 X 2K = 480 



4,656 4,656 



26,034 X 160 = 4,165,440 pounds. 
Weight of woodwork, weight per cubic foot taken as 40 pounds : 

2X8 

-j^ X 56.2 X 75 X 2 X 40 = 37,600 pounds of rafters. 

56.2 X 104 X 2 X H2 X 40 = 39,000 pounds of roof boards. 

80 X 100 X K2 X 40 = 53,500 pounds of floor boards. 
2 X 12 

^^^ X 80 X 75 X 40 = 40,000 pounds of roof joists. 

Total weight of woodwork = 170,100 pounds. 
Slate, weight per cubic foot taken as 170 pounds : 

56.5 X 104 X 2 X Ks X 170 = 41,600 pounds. 
Plaster, weight per cubic foot taken as 90 pounds : 

(360X30+80X40 + 100X56.2X2)^^ XH2X9O = 142,400 pounds. 
Air, weight per cubic foot taken as 0.08 pounds: 

(80 X 30 X 100 + 80 X 40 X 100)0.08 = 32,000 pounds. 
Heat required: 



'Seating and 

4,165,440 X 50 X 0.2100 = 43,737,000 B.t.u. 



170,100 X 50 X 0.5700 
41,600 X 50 X 0.2159 = 

142,400 X 50 X 0.2000 = 
32,000 X 50 X 0.2415 = 



Adding 15 per cent, for furnishings 



4,850,000 B.t.u. 

448,000 B.t.u. 
1,424,000 B.t.u. 

386,000 B.t.u. 



50,845,000 B.t.u. 
7,627,000 B.t.u. 



Total to raise to 50° 



58,572,000 B.t.u. 



The heating of the building structure may be very important in determining 
the size of the heating plant when a building is intermittently heated. 

7. First Law of Thermodynamics. — When mechanical energy 
is produced from heat a definite quantity of heat is used up 
for every unit of work done and, conversely, when heat is pro- 
duced by the expenditure of mechanical energy the same definite 
quantity of heat is produced for every unit of work spent. This 
first law of thermodynamics might also be called the law of the 
Conservation of Energy. The relation between work and heat 
has recently been determined with great accuracy and the 
results show that one British thermal unit is equivalent to 778 
foot-pounds. This factor is called the mechanical equivalent 
of heat or Joule's equivalent. 



Problems 

1. Convert 50°F. to degrees Centigrade. Convert 150°C. to degrees 
Fahrenheit. Convert 219°F. to degrees Centigrade. Convert 225°F. to 
absolute temperature on the Fahrenheit scale. 

2. A copper ball weighing 10 pounds is heated in a fire and immediately 
placed in a vessel of water having an equivalent water weight of 10 pounds. 
The water was raised in temperature from 50° to 100°. What was the 
temperature of the ball when it was removed* from the fire ? 



CHAPTER II 
HEAT LOSSES FROM BUILDINGS 

8. Sources of Heat Loss. — When the interior of any building 
is maintained at a temperature higher than that of the outside 
air there is a continual loss of heat from the building. The 
functions of a heating system are, first, to raise the temperature 
of the interior of the building to the point desired and, second, 
to maintain this temperature by supplying sufficient heat to 
replace that lost from the building. The determination of the 
amount of heat lost from the building under maximum condi- 
tions is the first step in designing the heating system. 

Before taking up the methods of calculating heat loss it is 
necessary to consider first the manner in which heat may be given 
up by any body. There are three ways in which heat can be 
transmitted from a body: by radiation, by conduction, and by 
convection. Each of these will be discussed separately. 

9. Radiation. — ^Heat is transmitted, or radiated, through space 
by what is supposed to be a motion or vibration of the ether which 
is believed to pervade all space. Radiant heat follows the same 
physical laws as radiant light, being radiated, like light, in 
straight lines. We may have heat ''shadows" just as we have 
hght shadows and the intensity of radiant heat is inversely 
proportional to the square of the distance from the source. 

Some substances are transparent to heat rays and others absorb 
them. Gases are almost perfectly transparent to radiant heat 
while such substances as wood, hair felt, and mineral wool are 
almost perfectly opaque to it. Radiant heat does not affect 
the medium through which it passes. When heat is radiated 
through the atmosphere, for example, the atmosphere is not 
perceptibly warmed by it. 

The rate at which heat is radiated increases as the absolute tem- 
perature of its source is raised. It has been determined experi- 
mentally that the amount of heat radiated from a body varies 
as the 4th power of the absolute temperature, or 

Qr = KT' 
9 



10 



HEATING AND VENTILATION 



in which Qr is the quantity of heat radiated, T the absolute tem- 
perature of the body, and K a constant depending upon the nature 
of the substance composing it. Radiant heat is given off by all 
bodies, the net amount of heat radiated by a body being the 
difference between the total amount radiated from it and the 
amount radiated from other bodies which is absorbed by it. 
If one body of absolute temperature Ti is surrounded by another 
body of the same material at temperature T2, then the heat which 
will pass between them is 



Qr = KTi^ - KT2' 



K{Ti^ 



V) 



This is known as Stefan's law. 

10. Conduction. — As has already been stated, heat will pass 
from any body to a body at a lower temperature which is 

brought into contact with it. 
It is further true that if one 
part of a body is at a higher 
temperature than another 
part there will be a flow of 
heat through the body. The 
transmission of heat in this 
manner is known as conduc- 
tion. A familiar example of 
this phenomenon is the flow 
of heat along an iron bar, one 
end of which is heated in a 
fire. The ability of different 
materials to conduct heat 
differs considerably. Metals are the best conductors of heat, 
while such materials as wood, felt, asbestos, etc., are very poor 
conductors. 

The conduction of heat which takes place through the walls of 
a building may be best understood from Fig. 2 in which PP is a 
plate, one side of which is enclosed by the walls WW. Let the 
temperature of the outside of the plate be 59° and let 60° be the 
temperature of the inside of the plate, of the inside walls WW, 
and of the inside air. Then all the heat that is lost by the room 
must be lost by conduction through the plate PP. The amount 
of heat lost will be dependent upon the material of the plate PP, 
upon the difference in temperature of its two sides, and upon its 
thickness. 




Fig. 2. 



HEAT LOSSES FROM BUILDINGS 11 

Let E = the ''specific conductivity" of the material. 

ti = the temperature of the warmer side of the plate. 

^2 = the temperature of the cooler side of the plate. 

A = the area of surface in square feet. 

I = the thickness of plate in inches. 

Q = the total quantity of heat transmitted. 



Then 



^ AE{ti - U) 



I 

AF 
the conductivity of the heat path is then —r- and the resistance 

of the heat path is its reciprocal -j^- 

Example. — Suppose a boiler plate, 5 feet square, and }4 inch thick, to 
have a temperature of 70° on one side and 200° on the other side. Assume 
the specific conductivity of the metal to be 240 B.t.u. per hour per square 
foot of area per inch in thickness per degree difference in temperature. 
The total heat transmitted per hour is then 

_ 25X240(200-70) , ^_^ nf^f,T>^ v 

Q = ~ = 1,560,000 B.t.u. per hour. 

>2 

11. Convection. — When a body is in contact with a fluid 
at a lower temperature, the envelope of fluid surrounding it 
becomes heated by conduction of heat from the body. As this 
fluid envelope is heated its density decreases and it is forced to 
rise, giving place to the colder fluid from below. A continuous 
current is thus created and maintained over the surface of the 
body. This process of heat transfer is called convection. It 
should be noted that the heat actually leaves the hot body by con- 
duction from its surface to the fluid in contact with it. The 
essential characteristic of the process of convection is the continu- 
ous renewal of the fluid layer at the surface of contact. 

The loss of heat from a body by convection is independent of 
the nature of the surface of the body, and of the material com- 
posing it, but is greatly affected by the form of the body, a 
cylinder and a sphere, for example, transmitting different amounts 
of heat per square foot of surface. The velocity of the fluid over 
the surface also affects the rate of heat transmission. In the 
case of convection by air the air movement is often produced 
by some external force, as when the wind blows against a building 
or when a fan in an indirect heating system forces air over the 
surface of steam coils. An increase in the velocity produces a 



12 HEATING AND VENTILATION 

more frequent renewal of the layer of air in contact with the 
body and augments the rate of heat transmission. 

Heat may also be transmitted from a fluid to a solid by con- 
vection as well as from a solid to a fluid. An example of this 
process is the transfer of heat from the warm air of a room to the 
cold outside walls. The air, upon giving up its heat, increases in 
density and falls, giving place to warmer air from above and 
producing a continuous downward current. 

12. Loss of Heat from Buildings. — The heat which is lost 
from a building may be divided into two parts : (a) the heat which 
passes by conduction through the building structure; and (6) 
the heat which is lost due to air infiltration. A third factor, the 
heat lost in warming air introduced for ventilation, might also 
be here mentioned. 

The heat which flows by conduction through the walls and 
roof of the building is transmitted from the outer surface of the 
structure partly by radiation and partly by convection. The 
calculation of the heat lost by convection is very difficult. 
Methods of arriving at the loss by convection from bodies of 
various shapes were developed by Peclet and are given in Box's 

Treatise on Heat, ' ' but these methods cannot, as a rule, be applied 
to the loss of heat from buildings. They assume, for example, 
that the air surrounding the object is, except for the influence 
of the heat from the body itself, in a perfectly quiescent state. 
In the case of buildings this is far from true, for the air surround- 
ing a building is always circulated more or less rapidly by the 
winds. Because of the necessity of taking into account variable 
factors of this nature, the heat loss from a building could not be 
stated in any simple expression and the practical rules that are 
used for such calculations are therefore largely empirical. The 
common method of treating the conduction of heat through 
building walls as given in the following pages was translated 
by J, H. Kinealy from the work of Rietschel and published in 
the Metal Worker. 

In the simplest form of building the walls consist of one solid 
piece of a single material and the transmission of heat takes place 
from the air of the room by convection, through the wall by con- 
duction, and from the outer surface of the wall by convection and 
by radiation. Such a wall is shown in Fig. 3. In order that heat 
may flow through the wall it is necessary that the room tempera- 
ture ti be higher than the temperature of the inside of the wall ti, 



HEAT LOSSES FROM BUILDINGS 



13 



that the temperature of the outside of the wall U' be lower than 
ti; and that the temperature of the outside air to be lower than U'. 
The amount of heat which will be transferred from the air of the 
room to a unit area of the wall will be ai (h — ti) in which a^ 
is a constant. The amount of heat flowing through a unit area 

of the wall will be — {ti — to') in which ei is a constant which 

represents the specific conductivity of the material composing 
the wall. Similarly the heat transfer from a unit area of the 
outside wall surface is ao (to' — to). 

When the rate of heat flow through the wall has reached a 
stable condition the quantity of heat flowing through successive 




points of the wall thickness must be the same and we have, 
therefore, 

ai(ti - ti') = ^{ti' - to') = aoW - to) 

A wall may be made up of a series of layers of different ma- 
terials, as shown in Fig. 4. The transmission of heat takes place 
in the same way except that the conductivity of the successive 
layers may be different. In a wall such as shown in Fig. 5 the 
heat passes through the inside wall to the air in the air space 
and thence through the outside wall to the outside air, the 
temperature at each successive point from the inside to the out- 
side being lower, as before. If ai, «£, as and ao are the constants 
representing the conductivity of heat between the air and the 
wall surfaces (Fig. 5) and ei and 62 are the specific conductivities 
of the materials composing the two walls, then the heat trans- 
mitted through the walls may be expressed in any of the following 
equal forms: 

aiiti - ti') = -' (ti' - t2') = a^it^' - « = aafe - t^") 

X 



- ^2 (f " 

- ~x, ^^' 



to ) — tto(^o — ^0) 



14 HEATING AND VENTILATION 

In order to use these expressions it would be necessary to know 
the temperature of all the wall surfaces. These temperatures 
are not known. The only known temperatures are the tempera- 
tures of the air inside the room and of the air outside of the build- 
ing. Therefore, let us assume that ' he heat transmission through 
the wall may be represented by ihe expression k(ti — ^o), in 
which fc is a constant to be determined. We then have for 
Fig. 3: 

k{ti - to) = aiih - ti') = ~ ih' - to) = ao{to' - to) 

X 

And for Fig. 5: 

^(^1 - ^o) = ai{ti - t^') = - it^' - t^') = a^{t2' - t2) 

Xi 

= a^{t2 - t2") = - {t^" - to') = aoW - to) 

X2 

Solving for k we have, for Fig. 3: 
J,- 1 

ai ei tto 

And for Fig. 5: 

j, = 1 

1 + ^1 + 1 + 1 _|_ ^2 _^ 1 (2) 

ai ei a2 as ei Gq 

X 

For thin glass or thin metal walls - is a very small quantity and 

may be neglected. 

The values of a and e must be known before k can be determined. 
The value of the convection factor, a, is determined by Grashof 
by the following equation: 

, , , (40c + 30(i)r 
a = c-\-d + — 1 po^-" 

in which c is a factor depending on the condition of the air, 
whether at rest or in motion. Rietschel gives the following 
values for c: 

Table III. — Values of c 

c 

Air at rest, air in rooms . 82 

Air with slow motion, air in rooms in contact with 

windows 1 . 03 

Air with quick motion, air outside of a building 1 . 23 



HEAT LOSSES FROM BUILDINGS 15 

The factor d depends upon the material composing the wall and on the con- 
dition of the surface. The values for d may be taken as follows: 

Table III. — Values of d 

Substance d Substance d 

Brickwork 0.74P " Sheet iron 0. 570 

Mortar and similar materials . 74( Sheet iron polished . 092 

Wood 0.740 Brass polished 0.053 

Glass 0.600 Copper 0.033 

Cast iron 0.650 Tin 0.045 

Paper 0.780 Zinc 0.049 

T is the difference between the temperature of the air and that 
of the surface of the wall. For walls composed of materials of low 
conductivity or very thick walls it may be taken as zero. In 
approximate calculations it is usually taken as zero. 

The following values of T are given by Rietschel : 

Table IV. — Values of T 

Brickwork 5 inches thick 14.4 

Brickwork 10 inches thick 12 . 6 

Brickwork 15 inches thick 10 . 8 

Brickwork 20 inches thick 9.0 

Brickwork 25 inches thick 7.2 

Brickwork 30 inches thick 5.4 

Brickwork 40 inches thick 1.8 

For single windows 36 . 

For double windows 18 . 

For wooden doors 1.8 

Table V gives values of e. These values, as given by different 
authorities, vary considerably. 

Table V. — Values of e 

e 

Brickwork 5 . 60 

Mortar, plaster 5 . 60 

Rubble masonry 14 . 00 

Limestone 15 . 00 

Marble, fine-grained 28.00 

Marble, coarse-grained 22.00 

Oak across the grain * 1 . 71 

Pine, with the grain 1 . 40 

Pine, across, the grain . 76 

Sandstone 10 . 00 

Glass 6 .60 

Paper 0.27 



16 



HEATING AND VENTILATION 



For example, assume a brick wall as shown in Fig. 6. There are 
four air contact surfaces and two walls through which conduction 
takes place, then: 

k is the same as in equation (2). 

Rietschel assumes ai, a2, and a^ equal and he uses the same 
value of T as for a solid of thickness equal to the brickwork with- 
out the air space. 



ai = a2 = as = 0.82 + 0.74 + 



(40 X 0.82 + 30X0.74)10 
10,000 



1.62 



ao= 1.23 + 0.74 + 



(40 X 1.23 + 30 X 0.74)10 
10,000 



2.04 




Fig. 6. 



Since both walls 


are 


of brickwork 






Xi 


4.75 






ei 


5.6 






X2 


8.25 






€2 


5.6 



= 0.85 



1.47 



Substituting in equation (2) 



1 



= 0.214 



0.62 + 0.85 + 0.62 + 0.62 + 1.47 + 0.49 

Making this same calculation, assuming T = 0, gives 

k = 0.210 

In Table VI are given the values of k for various building 
materials which have been determined either experimentally 
or by methods similar to the foregoing, by different author- 
ities. A more complete table of values of k is given in the 
Appendix. 



HEAT LOSSES FROM BUILDINGS 17 

Table VI. — Coefficients of Heat Transmission for Various 

Materials 

k 
B.t.u. per square foot, 
per hour per degree 
-rrT- 77 diflference in 

VvatLs: temperature 

Brick wall 4 inches thick, plain . 52 

Brick wall S}4 inches thick, plain . 37 

Brick wall 4 inches thick, furred and plastered . 28 

Brick wall 83^^ inches thick, furred and plastered 0.23 

Concrete wall 4 inches thick, furred and plastered 0.31 

Concrete wall 6 inches thick, furred and plastered .... . 30 
Clapboard wall with paper, sheathing, studding, and 

lath and plaster . 23 

Ceilings and Roofs: 

Lath and plaster, no floor above . 32 

Lath and plaster, single floor above 0.26 

Tin or copper roof on 1-inch boards . 45 

Shingle roof . 33 

Windows, Skylights and Doors: 

Ordinary windows 1 . 09 

Double windows . 45 

Single skyhght 1 . 50 

Pine door ^i inch thick . 47 

Oak door ^^ inch thick . 63 



13. Temperatures Assumed in Heating. — In determining the 
heat transmission through the walls of a building, it is necessary 
to assume certain temperatures for the outside air and for the 
inside air. In the latitude of New York City it is customary to 
assume 0° for the outside temperature. In the latitude of 
Washington it is customary to assume 20° above, and in the 
latitude of St. Paul 20° below. The assumed outside tempera- 
ture is ordinarily taken as the temperature which might exist 
for a period of at least 24 hours. The inside temperature to be 
assumed depends upon the type of building. The tempera- 
ture maintained in many classes of buildings is largely a matter 
of custom. In residences this temperature is higher in the United 
States than in any other country in the world, with the possible 
exception of Germany. In England and many other countries 
a temperature of from 55° to 60° is a perfectly proper temperature 
for a room; while in this country the temperature ordinarily 
ranges from 65° to 70°. 

The following are the inside temperatures usually assumed : 



18 



HEATING AND VENTILATION 



Table VII. — Inside Temperatures 

Degrees 

Residences 70 

Lecture rooms and auditoriums 65 

Factories for light work 65 

Factories for heavy work 60 

Offices and schools 68 to 70 

Stores 65 

Prisons 65 

Bathrooms 72 

Gymnasiums 55 to 60 

Hot houses 78 

Steam baths 110 

Warm air baths 120 

The following assumptions are ordinarily made for unhealed 
spaces: 

Table VIII 

Degrees 

Cellars and closed rooms 32 

Vestibules frequently opened to the outside 32 

Attics under a roof with sheathing paper and metal 

or slate covering 25 

Attics under a roof with paper sheathing and tile 

covering 32 

Attics under a roof with composition covering 40 

14. Heat Lost Due to Infiltration. — No building is ever air- 
tight; there is a large amount of leakage through the walls, the 
windows, and other openings. The amount of this infiltration 
depends largely upon how well the building has been constructed 
and upon the type of construction. For this reason no definite 
rule can be given for the determination of infiltration, and the 
allowance made for this loss must be a matter of judgment and 
experience. Usually the volume of infiltration is expressed as a 
certain ratio of the cubic contents, and experiments go to show- 
that the air of the average room is changed about once an hour 
because of infiltration. In rooms where doors are frequently 
opened to the outside, or where the windows are loosely fitted 
and the construction is faulty, the change of air may be as fre- 
quent as twice an hour. 

Strictly speaking, however, the amount of infiltration does not 
depend upon the volume of the room but upon the nature and 
size of the windows. Experiments^ have shown that the amount 

^ See "Window Leakage" by S. F. Voorhees and H. C. Meyer, Trans. 
A. S. H. & V. E., 1916. 



I 



HEAT LOSSES FROM BUILDINGS 19 

of air leakage varies considerably for different types of windows. 
Some forms of metal sash allow a large amount of leakage to 
take place. Weather strips are very effective in reducing air 
leakage. As the principal source of leakage is around the window 
sash the amount of leakage may be considered as varying 
directly with the perimeter of the windows. It is customary to 
assume a leakage of from 1.0 to 1.5 cubic feet of air per minute 
per foot of sash perimeter for windows equipped with weather 
strips. For windows without weather strips a considerably 
higher factor should be used. In large buildings the amount of 
infiltration should be computed in this manner, especially in the 
case of a tall or exposed building. 

The heat required to supply these infiltration losses must be 
sufficient to warm the air from the temperature of the outside 
air to that of the room. If the infiltration is figured on the basis 
of a certain number of air changes per hour the loss from this 
source may be expressed as follows : ' 
Let Ha = heat required per hour to supply loss due to infiltration. 

C — cubic contents of the room. 

n = number of changes per hour. 

tr = temperature of the room. 

^0 = temperature of the outside air. 

„ _ C(tr — U)n 
^" ~ 55.2 

The factor 55.2 = r> r>^i ^ ^^ r^^^^^r^ = heat required to raise 
U.z41o X U.U74y 

the temperature of 1 cubic foot of air 1° where 0.2415 is the 

specific heat of air at constant pressure and 0.0749 is the weight 

of a cubic foot of air at 70°. 

15. Heat Required for Ventilation. — The heat required for 
ventilation can easily be computed when the amount of air 
supplied per hour is known. 

Let H = heat required for ventilation. 

Q = quantity of air supplied in cubic feet per minute. 

Then, 

60 X Q{tr - to) 



H = 



55.2 



Besides supplying heat to replace that lost through the walls 
and by infiltration of air, a heating system must supply the heat 



20 HEATING AND VENTILATION 

which is stored in the structure and its contents and in the inside 
air. In heavy buildings the effect of the heat stored in the walls 
may have a material effect upon the amount of heat which must 
be supplied to warm the building initially. If the building is 
intermittently heated the effect is decidedly appreciable. The 
best illustration is in the cathedrals of Europe in which no heating 
systems are used and the heat stored in the walls during the 
summer serves to keep the building warm throughout the year. 

The heat which is required initially to warm the inside air and 
the building structure affects the rapidity with which the build- 
ing can be heated to the desired temperature. It is often 
desirable to investigate this question in designing a heating 
system which is to be operated intermittently and to increase the 
radiation, if necessary, so that the building can be warmed 
within a reasonable time. 

16. Calculation of Heat Loss from a Building. — In determining 
the heat loss from a room all surfaces should be considered which 
have on the outside a lower temperature than the temperature 
to be maintained in the room. If the room is over a portion of 
the basement which is unheated or below an unheated attic, the 
loss through the floor or ceiling should be considered. Similarly, 
if an adjacent room is liable to be unheated at times, the 
additional heat loss through the wall should be taken into 
account. Ordinarily it is assumed that there is no loss through 
inside walls where the surrounding rooms are heated. 

The conditions under which the room is to be used should be 
studied in determining the amount of heat necessary. In certain 
rooms such as restaurants in the basements of buildings, for 
example, where there are no outside windows, the problem is 
often one of cooling rather than heating. In designing any 
heating system, careful consideration should be given to the 
conditions existing, and to the exposure of each room in the 
building. 

The first step in computing the heat loss is to determine for 
every room the gross surface of exposed wall, and the window 
surface, from which the net wall surface is obtained by 
subtraction. The heat loss through the walls can then be 
computed from the expression, 

Hy, = Wkitr -to) 

in which 



HEAT LOSSES FROM BUILDINGS 21 

Hw — heat loss in B.t.u. per hour. 

W = exposed wall surface in square feet. 

tr = inside temperature. 

to = outside temperature. 

k = coefficient of heat transmission. 

A similar expression must be worked out for the walls, ceilings 
and floors next to unheated spaces. The value of U in such cases 
may be taken from Table VII. 

The heat loss through the glass surface is computed from the 
expression, 

Hg = Gk{tr - to) 

in which G is the area of the glass surface in square feet and k is 
the heat transmission for glass. 

The heat lost due to air infiltration is next determined by one of 
the methods given on pages 18 and 19. 

The total heat loss from the room in B.t.u. per hour is then 

H = Hw "1" Hg -\- Ha 

17. Correction Factors. — The heat losses determined by this 
method are for rooms not exposed to prevaihng winter winds. 

For exposed rooms it is customary to add certain percentages 
to the heat losses to allow for extreme exposures. Also, when a 
building is intermittently heated, an allowance should be made to 
insure that the building can be heated within a reasonable time. 
The correction factors commonly used are given in Table VIII. 

Table VIII. — Factors for Exposure and Intermittent Heating 

Percentage 
to be added 

For exposure in direction of prevailing winter winds (usually 

north and northwest) 15 

Same, severe conditions 20 

For west exposure 10 

For building heated during the day only and closed at 

night 15 

For buildings heated during the day and open at night 30 

For buildings heated intermittently 50 

18. Approximate Rules for Determining the Loss of Heat. — 

A common rule for the loss of heat from a building is that given 
by Prof. R. C. Carpenter in his book on ''Heating and Ventilation." 
This rule is developed from the following consideration: Refer- 
ring to Table VI we notice that 1 square foot of glass conducts 



22 HEATING AND VENTILATION 

approximately four times as much heat as a plastered brick wall 
4 inches thick. If, then, we divide the wall surface by 4, the 
result will give us the number of square feet of glass surface, which 
would lose the same quantity of heat. Adding to this the actual 
glass surface would give us the total equivalent glass surface. 
As the heat loss per square foot of glass surface per degree 
difference in temperature is approximately 1 B.t.u. per hour, 
this total equivalent glass surface multiplied by the temperature 
difference gives the heat lost through the walls. In considering 
the infiltration losses it is assumed that for ordinary-sized rooms 
the air in the room will be changed once an hour. One cubic 
foot of air weighs, approximately, Ks pound. To raise a pound 
of air 1° would require about 0.0183 B.t.u. or one heat unit will 
heat in round numbers about 55 cubic feet of air 1°. If, then, 
we divide the contents of a room by 55 we will have the heat lost 
by filtration through the walls per degree difference in temperature. 
Adding these factors together will give the total heat lost from the 
room. This rule may be concisely expressed as follows: 
Let H = B.t.u. loss per hour. 

G = glass surface in square feet. 

W = net exposed wall surface in square feet. 

C = cubic contents of room. 

n = number of times the air in the room is changed per hour. 

The quantity n ordinarily varies from 1 to 3; for ordinary 
rooms n = 1; for corridors 13-^; for vestibules 2 to 3. 

This rule will indicate an excessive heat loss where a room has 
large cubic contents and small window surface and will show heat 
losses that are too small where the room has a very large amount 
of exposed surface in proportion to its cubic contents. As the 
infiltration loss in a room depends upon the outside wall and 
window surface, the following rule seems somewhat more rational. 

Using the same notation as before, 

H = (^ + g) (tr - to)n 

where n is the infiltration factor. 

The factor n has been determined by comparison with many 
successful plants that have been installed and it has been found 
to vary from l}i to 2}^. For ordinary rooms n = l}i; for 



HEAT LOSSES FROM BUILDINGS 



23 



corridors n = 2; for vestibules and rooms where doors are opened 
frequently n = 2 to 2)^^. 

19. Heat Given Out by Persons and Processes. — In consider- 
ing the amount of heat necessary to heat a room attention must 
be given to the amount of heat that will be given off by the 
occupants of the room or by the processes which go on in it. But 
these sources of heat cannot always be depended upon, as it may 
sometimes be necessary to heat a room when there are no people 
in it or when the processes ordinarily going on are not in 
operation. On the other hand, it may be necessary to cool the 
room instead of heat it. Often in large auditoriums the greatest 
source of heat in a room are the people in it. The following table 
shows the heat given off by the human body under various 
conditions in a room at a temperature of 70°. 



Table IX 



Adults at rest 

Adults at work 

Adults at violent exercise , 

Children 

Infants 



B.t.u. per hour 

380 
450^ 
600' 
240 
63 



Example 1. — Assume a room, as 
shown in Fig. 7. Let the temperature 
be maintained in the room at 70°, 
the temperature of the outside air be 
0°. Let the walls be of brick, 18 inches 
thick, plastered on the inside, the win- 
dows be 23^ by 6 feet, the ceiling of 
the room be 10 feet high. Let the 
room be on the second floor of the 
building, the rooms above and below 
heated. The window surfaces are 
2 X 2M X 6 = 30 square feet. The 
gross wall surface is 20 X 10 = 200 
square feet. The net wall surface is 
200 - 30 = 170 square feet. The cubic 
contents is 20 X 14 X 10 = 2800 square 
feet. Then the heat lost from the room 
would be determined as follows. 

By the B.t.u. method: 



70' 



— 14 0' 



70 



70^ 



H^ = 170 X 0.24 (70 
Hg = 30 X 1.09(70 
„ 2800 (70 - 0) 

tia = 



55.2 



-0) 

-0) 

X 1.0 



H = 



70° 

Note: Windows 2-q"x 6-o' 
Fig. 7. 



= 2856 
= 2289 

3551 

8696 B.t.u. per hour. 



24 HEATING AND VENTILATION 

By Carpenter's rule: 



"=(■ 



= (50.9 + 42.5 + 30) X 70 

8638 B.t.u. per hour. 
By Allen's rule : 

H = (~^ + 3o) (70 - 0) 1.5 

= (42.5 + 30) X 70 X 1.5 

= 7613 B.t.u. per hour. 

Problems 

1. Compute the value of k for a wall consisting of 2 inch pine boards. 
Assume T = 3. 

2. Compute the heat loss per hour, per square foot of area, of a wall 
consisting of two thicknesses of 1 inch pine boards with an air space of 2 
inches between. Room temperature 60°, outside temperature 10°. Assume 
T = 1.8. 

3. Compute the heat loss per hour, per square foot of area, of a wall 
consisting of 1 inch oak boards, an air space of 1 inch, and 4 inches of 
brickwork. 

4. In the room of Fig. 7 (Example 1) find the percentage of the heat loss 
which would be saved during a heating season of 8 months if double windows 
were used. Assume average temperature of the room and the surrounding 
rooms to be 65° and the average outside temperature to be 40°. 

5. Taking the same room as in Example 1, heated to a temperature of 60°, 
with the surrounding rooms at 70° and the air outside at 10°, how much 
heat must be supplied to the room per hour? Inside walls are of lath and 
plaster. Ceihng is of lath and plaster, with single floor above, and the room 
below has its ceiling plastered. 

6. Take the same room as Example 1, except that the room is covered 
by a flat tin roof. The air space between the ceiling of the room and roof 
should be assumed to be at a temperature of 32°. 



CHAPTER III 
DIFFERENT METHODS OF HEATING 

20. Classification of Heating Systems. — The different types 
of heating systems may be classed under two general heads: 
direct and indirect. In direct heating the heating surfaces are 
placed in the rooms to be heated. Under this head come grates, 
stoves, steam radiators, and hot-water radiators. In indirect 
heating systems the heating surfaces are placed outside the rooms 
to be heated and air passes over them, is heated, and flows to the 
various rooms through pipes or flues. Hot-air furnaces would be 
included under this head, together with various systems of heating 
in which fresh cold air is made to pass over steam or hot-water 
radiators on its way to the rooms. 

Indirect systems may be subdivided into two classes : those in 
which the air circulates by gravity and those in which the cir- 
culation is produced by a fan or some other mechanical device. A 
good example of the gravity or '' natural" systems is the hot-air 
furnace in which the circulation of air through the furnace and 
air ducts is produced by the difference in temperature, and con- 
sequently in density, between the air in the hot-air ducts and the 
cold air outside. The fan systems of heating used in schools 
and churches are examples of the forced-circulation type in which 
the circulation is produced by a disc fan or a pressure blower. 
Before studying the design of the various systems of heating 
it is desirable to understand in general their advantages and 
disadvantages. 

21. Grates. — The most primitive form of heating apparatus is 
the grate. In the grate the air which passes through the fire, and 
is heated by the fire, all passes up the chimney and only the heat 
given off by radiation to the walls and objects in the room and 
the small amount given off by the chimney walls is effective in 
heating the room. In grates of better construction this condition 
is somewhat improved by surrounding the grate with firebrick so 
arranged that it becomes highly heated and radiates heat to the 
room. But the fact that all the air heated by the grate passes up 

25 



26 HEATING AND VENTILATION 

the chimney makes the grate a very uneconomical form of heat- 
ing. In the best forms of open grates only about 20 per cent, of 
the heat of the fuel is effective in heating the room. This 
form of heating, however, is highly recommended by many and 
is a very popular method of heating throughout England and 
Scotland. The feeling of a grate-heated room is quite different 
from that of a room heated by other means. All of the heat is 
given off by radiation and the air is at a considerably lower 
temperature than the objects in the room, owing to the fact 
that the radiated heat does not heat the air through which it 
passes. The air of the room being at a much lower temperature, 
its capacity for moisture is not increased as much as it would be 
were the air heated to a higher temperature. The result is 
that the air contains proportionately more moisture than is the 
case with most other forms of heating, which, no doubt, is an 
advantage. On the other hand, it is impossible to heat the room 
uniformly and a person is either hot or cold, depending on his 
distance from the fire. Heating by means of grates is practised 
only in the more moderate climates. Grates are useful in houses 
heated by other means, as the open chimney forms a most effi- 
cient foul-air flue and greatly improves the ventilation. 

22. Stoves. — The stove is a marked improvement over the grate, 
particularly from the standpoint of economy. The modern base- 
burner stove is one of the most efficient forms of heating appara- 
tus, making use of from 70 to 80 per cent, of the heat in the fuel. 
In heating a room, the hot surface of the stove, being at a higher 
temperature than that of the surrounding objects in the room, 
radiates heat directly to those objects. In addition, heat is 
given to the air of the room by contact with the hot surface of 
the stove. In selecting a stove to heat a given room care should 
be taken to choose one of ample size so that only in the coldest 
weather would it be necessary to keep the drafts wide open in order 
to heat the room. At the present time the stove as a general 
source of heat is being rapidly discarded because of the attendance 
required, the space occupied, the unsightly appearance of the stove, 
and the fact that a separate stove is required in every room for 
satisfactory results. Another objection to the stove is the fact 
that it does not provide ventilation to the room which it heats. 

23. Hot-air Furnaces. — The hot-air furnace is the natural 
outgrowth of the stove. In this system one large furnace is 
placed in the basement of the building, and the air is taken 



I 



DIFFERENT METHODS OF HEATING 27 

from the outside or recirculated from the house, passed over the 
surfaces of the furnace, and carried up through the flues to the 
rooms to be heated. The principle advantages of the hot-air 
furnace are that it provides a cheap method of furnishing both 
heat and ventilation, requires little attendance, and does not 
deteriorate rapidly when properly taken care of. The greatest 
disadvantage of this system is that the circulation of the heated 
air depends entirely upon natural draft; that is, it depends upon 
the difference in weight between the air inside the flues and the 
air outside the flues. This difference is extremely small, so 
that the force producing circulation in the flue is always small. 
When a very strong wind blows against one side of the house, 
air from the outside enters through the window cracks and other 
small openings, forming a slight pressure in the rooms and pre- 
venting the warm air from entering, thus making it difficult 
to heat the rooms on that side of the house. If the system is 
carefully designed, however, this difficulty can be overcome 
in a measure. Another serious objection to the hot-air furnace 
is that it is seldom dust-tight, and dust, ashes, and gases from the 
fire are carried into the rooms. In general, the hot-air furnace 
may be considered as a very good type of heating plant for 
small residences, but because of the small force available for 
producing circulation its use is limited to buildings where the 
length of the horizontal flues does not exceed 15 feet. 

In the case of the hot-air furnace, the heat is carried from the 
furnace by the air which passes around the furnace and then 
enters the rooms through the flues. This air circulates in the 
room and heats the contents of the room and supplies the heat 
which is lost through the walls. The economy of the hot-air 
system will vary, depending on the relative proportions of the 
air taken from the outside and from the rooms. If the air enter- 
ing the furnace is taken from the house and not from the outside, 
the economy of the hot-air furnace will be about the same as 
that of the steam system. If, however, cold air be taken from 
the outside, an additional amount of heat will be used in heating 
this cold air up to the temperature of the rooms. Control of 
the heat supply, with a hot-air furnace, is readily obtained by 
adjusting the dampers at the registers in each room and by 
manipulating the furnace drafts. 

24. Direct Steam Heating. — From the standpoint of ventila- 
tion, direct steam heating, without other means for ventilation. 



28 HEATING AND VENTILATION 

is not as desirable as the hot-air furnace. Mechanically, how- 
ever, it has many advantages. The modern radiator is easily 
adapted to almost any location in the room and its operation 
is not affected by the winds. The circulation of the system is 
positive and a distant room can be heated as easily as those 
close to the boiler. 

In the older forms of direct steam-heating systems control 
of the heat supply is difficult because the radiators, being 
large enough to heat the room on the coldest days, give off 
too much heat for average conditions. Since the entire radia- 
ting surface is heated to a high temperature when the radiator 
is turned on, much manipulation of the valves is required 
in order to keep the room at a comfortable temperature. In 
recent years these disadvantages have been overcome in the so- 
called ''vapor" systems which make use of steam at pressures 
but slightly higher than atmosphere, and in some cases below 
atmosphere. In these systems the steam supply to each radia- 
tor can be controlled at the inlet valve so that only the quantity 
actually required is admitted to the radiator, and much better 
regulation is therefore possible. The efficiency of the direct 
steam-heating system in a well-designed plant is from 60 to 70 
per cent. 

25. Direct Heating by Hot Water. — The appHcation of direct 
hot-water radiators as a method of heating is similar to that 
of steam, with the exception that the surfaces are usually at 
a much lower temperature and more radiating surface is there- 
fore required. Hot-water systems are preferable to ordinary 
steam systems in that the temperature of the radiating surfaces 
can be easily controlled, and can be anywhere from the tem- 
perature of the room to 190°, or even higher in the case of 
certain forms of hot- water systems. Another advantage is that 
the surface of the radiator, being at a lower temperature, gives 
off more heat by convection and less by radiation, which tends 
to keep the room at a more uniform temperature throughout 
and makes it more comfortable to the occupants. The principal 
disadvantage of the hot-water system lies in the fact that the 
circulation of the system is ordinarily produced only by the 
difference in weight between the water in the hot leg of the system 
and that in the cold leg of the system. The difference in tem- 
perature between the two legs is small, being usually about 10° 
to 20°, so that the resulting force producing circulation is there- 



DIFFERENT METHODS OF HEATING 29 

fore small. It is necessary to be very careful in designing the 
piping for a hot-water system as the circulation may be easily 
affected by the friction in the piping and the height of the radia- 
tor above the boiler. The greater the height above the boiler 
the greater will be the difference in weight between the two col- 
umns of water and the stronger will be the force producing cir- 
culation. This system in general requires more careful design 
and construction than the steam system. Another disadvantage 
is that, because of the great thermal capacity of the water con- 
tained in the system, considerable time is necessary to change 
its temperature and the system cannot be made to respond 
quickly to sudden changes in the demand for heat. The effi- 
ciency of the hot-water system is practically the same as that of 
a steam system and we may expect to obtain in the rooms about 
60 or 70 per cent, of the heat in the fuel. 

Where hot-water heating is used in large buildings the circula- 
tion is produced by a pump. The difficulty of circulation is 
then done away with and the flow of water is certain and rapid. 

26. Indirect Steam and Hot-water Heating by Natural Circu- 
lation. — In heating with indirect steam or water radiation 
cold air is drawn from the outside, passed through and around 
the hot radiator, which is usually situated in the basement, and 
dehvered through flues to the rooms to be heated. The rules 
governing the introduction of air into the rooms and the 
method of running the pipes are similar to those employed in 
the installation of the hot-air furnace. The principal advantages 
of indirect steam and water heating over the hot-air furnace 
are that each room has a separate source of heat, the system is 
not affected by the winds, and no dust or obnoxious gases are 
carried to the rooms. The source of heat being independent of 
the position of the boiler, it is possible to place the indirect 
radiators anywhere in the building and long air flues are not 
necessary. This makes the indirect radiator much more certain 
in operation than the hot-air furnace. The application of in- 
direct hot-water radiators is similar to that of steam radiators 
and the economy is practically the same, although the use of 
hot water for indirect heating has been much more limited than 
the use of steam. The installation of hot-water radiators must 
be done with great care so that each radiator will at all times have 
the proper amount of water circulating through it, for if for any 
reason the circulation is stopped the water in the radiator will be 



30 HEATING AND VENTILATION 

in danger of freezing. In mild climates this difficulty would not 
be as serious as in locations where the weather is extremely cold. 

27. Fan Systems of Heating. — In buildings of a public or 
semi-public character, where a large number of people are 
gathered in a relatively small space, it is necessary to provide 
adequate ventilation. With the systems that have been pre- 
viously described it is impossible to introduce sufficient quanti- 
ties of air to ventilate such buildings properly. It may be said 
in general that no system of natural circulation has ever produced 
satisfactory ventilation in a room occupied by a large number of 
people; it is necessary to provide some mechanical means for 
introducing the air. In fan systems the pressure produced by 
the fan makes the circulation positive so that it is not affected 
by winds or by the distance of the room from the source of heat. 
The air is taken from the outside, or sometimes recirculated from 
the inside, and is passed through the heating coils and forced 
into the building by the fan. 

There are three general methods of heating and ventilating 
with the fan system. In one system the air is first passed through 
a tempering coil and then taken by the fan and delivered through 
a heating coil. Each room has a connection both to the hot air 
and to the tempered air chambers. The temperature of the air 
in the room is adjusted by taking the air partly from the hot-air 
chamber and partly from the tempered-air chamber. In the 
second system the rooms themselves are heated by means of 
direct radiation and the fan delivers air to the rooms only for 
the purpose of ventilation. In this case a much smaller amount 
of heating surface in the fan system is necessary as the air is 
heated to only about 70°. The economy of this system is also 
better, due to the fact that it is necessary to run the fan only 
when it is necessary to ventilate the building. 

In the third system both the heating and ventilating is done by f 

means of the fan system but only one system of ducts is installed. ) 

The temperature of the air leaving the heating coils is adjusted 
so as to maintain the proper room temperature. This method 
is applicable only in factory buildings, theatres, and other build- 
ings which are divided into only a few rooms, making it possible 
to utilize air of the same temperature throughout the entire 
building. 

28. Combinations of Different Systems. — In addition to the 
combination just described, of direct radiation and fan ventila- 



DIFFERENT METHODS OF HEATING 31 

tion, there have been devised innumerable combinations — com- 
binations of direct and indirect steam systems, direct and in- 
direct hot water, water and hot air, and steam and hot air. 
The combinations which have been most used are those of direct 
and indirect steam systems and of hot water and hot air. 

29. Economy of Heating Systems. — The economy of any heat- 
ing system depends upon the completeness with which the heat 
in the fuel is effectively utilized in heating the building. The 
principal sources of loss and the manner in which the heat is 
utilized in any type of heating system are as follows : 

Losses: 

Imperfect combustion. 

Sensible heat in the chimney gases. 

Combustible in the ash. 

Radiation from boiler or furnace. 

Radiation from flues or piping. 

Losses through excessive temperature in the building. 

HeM utilized: 

Heat utilized in supplying the heat losses from the building. 
Heat used for ventilation. 

Of the losses, the first three are dependent rather upon the 
design of the grates and firepot than upon the type of heat- 
ing system. The radiation from the boiler or furnace is 
partially recovered as it serves to warm the basement and de- 
creases the heat loss to the basement from the rooms above. 
The loss from this source is fairly constant, regardless of the 
amount of heat delivered by the boiler or furnace and if a very 
low fire is carried, as in mild weather, it may become quite 
appreciable in comparison with the heat delivered. The loss 
from the flues or piping is also partially utilized in warming the 
building. 

The heat used to supply the heat losses from the building is the 
principal product of any heating system. A part of this heat 
may be considered as a loss, however, if excessive temperatures 
are maintained either during the hours when the building is 
occupied, or during the night or other times when a low tempera- 
ture could be carried. 

The amount of heat used for ventilation will depend upon the 
amount of fresh air supplied. The air introduced for ventilation 
is discharged from the building at room temperature, and the 
heat contained in this air in excess of the heat in the outside air 



32 HEATING AND VENTILATION 

is evidently the amount chargeable to ventilation. While this 
item might, from the standpoint of heating only, be considered 
as a loss, it is really the price that must be paid for good ventila- 
tion which is essential to health and comfort. In many States 
there are laws which specify the minimum amount of air which 
must be furnished per hour for each occupant in theatres and 
other buildings of a public character. The necessity and impor- 
tance of ventilation will be discussed in later chapters. 



< 



(I 



CHAPTER IV 
PROPERTIES OF STEAM 

30. The Formation of Steam. — The different types of heating 
systems discussed in the previous chapter owe most of their 
characteristic features to the element used to transmit the heat 
from the boiler or furnace to the rooms. The most important 
is the steam system in which steam serves as the medium for 
carrying the heat from the boiler to the radiators. Before tak- 
ing up the design of steam-heating systems it is necessary to 
study the nature and properties of steam. 

Steam as produced in the ordinary boiler contains a certain 
amount of water in suspension as does the atmosphere in foggy 
weather. Let us suppose that we have a boiler partly filled with 
cold water, and that heat is applied to the outside of the boiler. 
As the water in the boiler is heated its temperature slowly rises 
until a certain temperature is reached at which small particles 
of water are changed into steam. The steam bubbles rise through 
the mass of water and escape from the surface. The water is 
then said to boil. The temperature at which the water boils 
depends entirely upon the pressure in the boiler. The steam 
produced from the boiling water is at the same temperature as 
the water, and under this condition the steam is said to be 
saturated. If we close the steam outlet the pressure in the boiler 
and the temperature of the water and steam will increase rapidly. 
If we continue to apply heat to the boiler with the outlet partly 
closed so that a constant pressure is maintained, the temperature 
of the steam and water will remain constant until all of the water 
is evaporated into steam. Any further addition of heat will 
raise the temperature of the steam above the boiling point and 
it will then be superheated. 

31. Superheated Steam. — Superheated steam is steam at a 
temperature higher than the temperature of the boiling point 
corresponding to the pressure. If water were to be intimately 
mixed with superheated steam some of the heat in the steam 
would be used in evaporating the water and the temperature of 
3 33 



34 HEATING AND VENTILATION 

the steam would be lowered. If sufficient water were added the 
superheat would be entirely used up in evaporating the water and 
the steam would then be saturated. Superheated steam can 
have any temperature higher than that of the boiling point. 
When raised to any temperature considerably above the boiling 
point it follows very closely the laws of a perfect gas and may be 
treated as a perfect gas. 

32. Saturated Steam. — When steam is at the temperature of 
the boiling point corresponding to its pressure it is said to be 
saturated. If this saturated steam contains no suspended mois- 
ture it is said to be dry saturated steam, or in other words, dry 
saturated steam is steam at the temperature of the boiling point 
and containing no water in suspension. If heat is added to dry 
saturated steam, not in the presence of water, it will become super- 
heated. If heat is taken away from dry saturated steam it will 
become wet steam. The steam used in a heating plant is saturated 
steam and nearly always contains moisture, so that the substance 
used as a heating medium is really a mixture of steam and water. 
Bteam at a pressure equal to or slightly above atmosphere is 
commonly known as vapor. It should be remembered, however, 
that the difference between vapor and steam is merely one of 
pressure, and that vapor is in no sense a separate state of the 
substance. Dry saturated steam is not a perfect gas and the 
relations of its pressure, volume, and temperature do not follow 
any simple law but have been determined by experiment. The 
properties of dry saturated steam were originally determined by 
Regnault between 60 and 70 years ago, and so carefully was his 
work done that no errors in his results were apparent until within 
very recent years, when the great difficulty of obtaining steam 
which is exactly dry and saturated became appreciated, and new 
experiments by various scientists proved that Regnault's results 
were slightly high at some pressures and slightly low at others. 

33. Properties of Steam. — The heat used in the formation of 
1 pound of superheated steam at any pressure from water at 
32° may be divided into three parts : (a) the heat of the liquid, which 
is the heat required to raise the temperature of the water from 
32° to the temperature of the boiling point; (b) the latent heat 
of vaporization, which is the amount required to change the 1 
pound of water at the temperature of the boihng point to dry 
saturated steam at the same temperature; and (c) the ''heat of 
superheat "or, more simply, the superheat, which is the heat added 



i 



PROPERTIES OF STEAM 35 

to 1 pound of steam to raise it from the boiling point temperature 
to the final temperature. 

34. Heat of the Liquid. — The heat of the liquid may be deter- 
mined for any boihng point temperature by the expression 

h = c(t- 32) 
in which 

h = the heat of the liquid. 

t = the boiling point temperature. 

c = the specific heat of water. 
For approximate results c may be taken as = 1 . The change in 
the volume of the water during the increase in temperature is 
extremely small, and the amount of external work done may be 
neglected and all of the heat of the liquid may be considered as 
going to increase the heat energy of the water. 

The heat of the liquid, together with the other properties of 
saturated steam, is given in Table X for various steam pressures. 
This table is condensed from Marks and Davis' complete tables 
which are generally .accepted as being accurate. 

35. Latent Heat. — The latent heat of steam has been defined as 
the heat required to convert 1 pound of water at the temperature 
of the boiling point into dry saturated steam at the same tem- 
perature. Experiments show that the latent heat, usually 
designated by L, diminishes as the pressure increases. 

When water is changed into steam, the volume is greatly 
increased^ so that a considerable portion of the latent heat is 
used in doing external work. The remainder may be considered 
as being utilized in changing the physical state of the water. 
Let P be the pressure at which the steam is generated , V the volume 
of 1 pound of steam, and v the volume of 1 pound of water; 
then the external work done is equal to 

P(V - v) 

At 212° the external work done in producing 1 pound of steam is 
equivalent to 73 B.t.u. or about one-thirteenth of the latent 
heat. 

Experiments show that the latent heat of steam diminishes 
about 0.695 heat units for each degree that the temperature of the 
boiling point is increased. If t be the temperature of the boiling 
point, then, approximately, 

L = 1072.6 - 0.695(^ - 32) 



36 HEATING AND VENTILATION 

When steam condenses the same amount of heat is given up as 
was required to produce it. 

36. Total Heat of Steam.— The total heat of dry saturated, 
steam is the heat required to change 1 pound of water at 32° 
into dry saturated steam. This quantity will be designated by 
H, and 

H = h-\-L 

The experimental results given in the table for the value of the 
total heat may be approximated very closely by means of the 
formula 

H = 1072.6 + 0.305(^ - 32) 

It is more accurate, however, to take the values of the total heat 
from the tables than it is to compute them from the formula. 
The total heat in 1 pound of steam under any condition of mois- 
ture or superheat is the amount of heat required to change it 
from water at 32° to its existing condition. 

When steam contains entrained water the percentage by weight 
of dry steam in the mixture is termed the quality of the steam. 
If we let q represent the quality of the steam, then the latent heat 
in 1 pound of wet steam equals 

100 
and the total heat in 1 pound of wet steam equals 

^^ 100 

37. Steam Tables. — The following table shows the properties 
of dry saturated steam. More complete tables will be found in 
Marks and Davis' ''Steam Tables" and in the engineering 
handbooks. Column 1 gives the absolute pressure of the steam 
in pounds per square inch. Absolute pressure is the pressure 
shown on the steam gage plus the atmosphere or barometric 
pressure. For sea-level barometer the atmospheric pressure is 
14.7 pounds per square inch. Column 2 gives the corresponding 
temperature of the steam in degrees Fahrenheit. Column 3 gives 
the heat of the liquid, and column 4 gives the latent heat. Column 
5 gives the total heat of the steam and is the sum of the quantities 
in columns 3 and 4. Column 6 is the volume of 1 pound of dry 
saturated steam at the different pressures. Column 7 is the 
weight of 1 cubic foot of steam at the different pressures. 



PROPERTIES OF STEAM 



37 



Table X. — Properties of Saturated Steam^ 



1 

Absolute 

pressure, 

lb. per 

sq. in. 


2 
Temp., 
deg. F. 


3 

Heat 
of the 
liquid 


4 
Latent 
heat of 
evap. 


5 

Total 

heat of 

the steam 


6 
Sp. vol., 
cu. ft. 
per lb. 


7 

Density, 

lb. per 

cu. ft. 


V 


t 


h 


L 


H 


V 


\/v 


10 


193.22 


161.1 


982.0 


1,143.1 


38.38 


0.02606 


11 


197.75 


165.7 


979.2 


1,144.9 


35.10 


0.02849 


12 


201.96 


169.9 


976.6 


1,146.5 


32.36 


0.03090 


13 


205.87 


173.8 


974.2 


1,148.0 


30.03 


0.03330 


14 


209 . 55 


177.5 


971.9 


1,149.4 


28.02 


0.03569 


15 


213.00 


181.0 


969.7 


1,150.7 


26.27 


0.03806 


16 


216.30 


184.4 


967.6 


1,152.0 


24.79 


0.04042 


17 


219.40 


187.5 


965.6 


1,153.1 


23.38 


0.04279 


18 


222.40 


190.5 


963.7 


1,154.2 


22.16 


0.04512 


19 


225.20 


193.4 


961.8 


1,155.2 


21.07 


0.04746 


20 


228.00 


196.1 


960.0 


1,156.2 


20.08 


0.04980 


21 


230.60 


198.8 


958.3 


1,157.1 


19.18 


0.05213 


22 


233.10 


201.3 


956.7 


1,158.0 


18.37 


0.05445 


23 


235.50 


203.8 


955.1 


1,158.8 


17.62 


0.05676 


24 


237.80 


206.1 


953.5 


1,159.6 


16.93 


0.05907 


25 


240.10 


208.4 


952.0 


1,160.4 


16.30 


0.0614 


30 


250.30 


218.8 


945.1 


1,163.9 


13.74 


0.0728 


35 


259 . 30 


227.9 


938.9 


1,166.8 


11.89 


0.0841 


40 


267.30 


236.1 


933.3 


1,169.4 


10.49 


0.0953 


45 


274 . 50 


243.4 


928.2 


1,171.6 


9.39 


0.1065 


50 


281.00 


250.1 


923.5 


1,173.6 


8.51 


0.1175 


55 


287.10 


256.3 


919.0 


1,175.4 


7.78 


0.1285 


60 


292 . 70 


262.1 


914.9 


1,177.0 


7.17 


0.1394 


65 


298.00 


267.5 


911.0 


1,178.5 


6.65 


0.1503 


70 


302.90 


272.6 


907.2 


1,179.8 


6.20 


0.1612 


75 


307.90 


277.4 


903.7 


1,181.1 


5.81 


0.1721 


80 


312.00 


282.0 


900.3 


1,182.3 


5.47 


0.1829 


85 


316.30 


286.3 


897.1 


1,183.4 


5.16 


0.1937 


90 


320.30 


290.5 


893.9 


1,189.4 


4.89 


0.2044 


95 


324.10 


294.5 


890.9 


1,185.4 


4.65 


0.2151 


100 


327.80 


298.3 


888.0 


1,186.3 


4.429 


0.2258 


105 


331.40 


302.0 


885.2 


1,187.2 


4.230 


0.2365 


110 


334.80 


305.5 


882.5 


1,188.0 


4.047 


0.2472 


115 


338.10 


309.0 


879.8 


1,188.8 


3.880 


0.2577 


120 


341.30 


312.3 


877.2 


1,189.6 


3.726 


0.2683 


125 


344.40 


315.5 


874.7 


1,190.3 


3.583 


0.2791 


130 


347.40 


318.6 


872.3 


1,191.0 


3.452 


0.2897 


135 


350.30 


321.7 


869.9 


1,191.6 


3.331 


0.3002 



38. Mechanical Mixtures. — Problems involving the resulting 
temperature and final condition when various substances at 

1 From Marks and Davis' "Steam Tables and Diagrams." 



38 HEATING AND VENTILATION 

different temperatures are mixed mechanically are often met 
with in heating work. They are best treated by first determining 
the heat in B.t.u. that would be available for use if the temperature 
of all of the substances were brought to 32°F., and using this 
heat (positive or negative) to raise (or lower) the total weight 
of the mixture to its final temperature and condition. Another 
method of solving such problems is by equating the heat ab- 
sorbed to the heat rejected and solving for t, the resulting tem- 
perature. It is often difficult to decide upon which side of the 
equation a material should be placed. In such a case a trial cal- 
culation should be made, and the temperature determined by 
the trial will settle this question. 

In. a mixture of substances which pass through a change of 
state during the mixture process it is almost necessary to make a 
trial calculation. Take for example a mixture of steam with 
other substances. The steam may all be condensed and the 
resulting water cooled also; the steam may be condensed only; or 
the steam may be only partially condensed. The equations 
in each case would be different. 

If 1 pound of dry- saturated steam at a temperature ti is con- 
densed and then the temperature of the condensed steam is 
lowered to a temperature ^2, the amount of heat H^ given off 
would be 

H' =Li + c{h - h) 

where Li is the latent heat corresponding to the temperature h 
and c is the specific heat of water. If the steam were condensed 
only, the heat given off would be 

H' = Li 

and the temperature of the mixture is the temperature corre- 
sponding to the pressure. If the steam is only partly condensed 
let q' equal the per cent, of steam condensed. Then 

H^ - ^^ 
^ 100 

and the temperature of the mixture is the temperature corre- 
sponding to the pressure. 

The general laws of thermodynamics do not apply in the case 
of mixtures as the equations become discontinuous. 

The general expression for heat absorbed in passing from a 
solid to a gaseous state may be stated as follows: 



PROPERTIES OF STEAM 39 

Let Ci, C2, C3 be the specific heats of the material in the solid, 
liquid, and gaseous states, respectively. Let w be the weight of 
the material, t the initial temperature, ti the temperature of the 
melting point, ^2 the temperature of the boiling point, ts the final 
temperature, Hf the heat of Hquefaction, and L the heat of 
vaporization. Then 

H' = wMh - t) + Hf+ C2{t2 -ti)+L+ csih - t2)] 

Example. — Find the final temperature and condition of the mixture 
after mixing 10 pounds of ice at 20°, 20 pounds of water at 50° and 2 pounds 
of steam at atmospheric pressure. Mixture takes place at the pressure of 
the steam. The specific heat of ice may be taken as 0.5 and the heat of 
liquefaction as 144 B.t.u. 

First Method 
Solution. — 
Heat to raise ice to 32° = 10 X 0.5(32 - 20) =60.0 

Heat to melt ice = 10 X 144 = 1440 



Total heat necessary to change the ice to water at 32° = 1500 B.t.u. 

Heat given up by water when temperature is lowered to 

32° = 20 X (50 - 32) = 360.0 

Heat in steam above 32° (from tables) = 2 X 1150.3 = 2300.6 



Total heat given up in lowering water and steam to 32° = 2660.6 B.t.u. 

Heat available for use = 2660.8 - 1500 = 1160.6 B.t.u. 

Degrees this heat will raise the mixture 1160 . 6 ^32 = 36 . 3 

.•. Final temperature of mixture = 36.3 + 32 = 68.3°F. 
Ans. 32 pounds water at 68.3°F. 

Second Method 

Assume that the steam is all condensed and that the final temperature 
of the mixture is t. Then the heat necessary to raise the ice to the melting 
point equals 

10 X 0.5(32 - 20) 

The heat necessary to melt the ice equals 10 X 144; the heat necessary to 
raise the melted ice to the temperature of the mixture equals 10 (^ — 32); the 
heat necessary to raise the water to the temperature of the mixture equals 
20 (^ — 50); the heat given up by the steam in changing to water at the 
temperature of the boiUng point equals 2 X 970.4, and the heat given up 
by the condensed steam when its temperature is lowered to the temperature 
of the mixture equals 2(212 — t). 

Combining the preceding parts into one equation, we have 

10X0.5(32 -20) +10X144 + 10(^-32) +20(« -50) =2X970.4+2(212-f) 



40 HEATING AND VENTILATION 

60 + 1440 + 10/ - 320 + 20t - 1000 = 1940.8 + 424 - 2t 

S2t = 2184.8 
t = 68.3° 

Since t is less than the temperature of the boiling point corresponding to 
the pressure at which the mixture takes place, all the steam is condensed. 
Ans. 32 pounds water at 68.3°F. 

Example. — Find the resulting temperature and condition after mixing 10 
pounds of ice at 20°, 20 pounds of water at 50°, 40 pounds of air at 82°, and 
20 pounds of steam at 100 pounds gage pressure and containing 2 per cent, 
moisture. Mixture takes place at the pressure of the steam. 

First Method 

Solution. — 
10 X 0.5(32 - 20) = 60 

10 X 144 ' = 1440 



1500 B.t.u. = heat to raise ice to water at 
32°. 
20 X (50 - 32) = 360 

40 X 0.2415(82 - 32) = 483 
20(308.8 + 0.98 X 880.0) = 23,424 



24,267 B.t.u. = heat given up by air, water, 
1,500 and steam. 



22,767 B.t.u. = heat available. 
40 X 0.2415(337.9 - 32) = 2,955 B.t.u. = heat to raise air to 337.9°. 



19,812 B.t.u. = heat available to raise the 
water. 
50 X 308.8 - = 15,440 B.t.u. = heat to raise water to 337.9°. 



4,372 B.t.u. = heat available to evaporate 

water. 
4372 
^^7^0 = 4.97 pounds steam. 

Ans. 40.00 pounds air ^ 

45.03 pounds water \ at 337.9°. 

4.97 pounds dry saturated steam J 

Second Method 

Assume the steam to be all condensed and let the temperature of the 
mixture be t°. Equating the heat gained by the ice, water, and air, and the 
heat lost by the steam, we have 

10 X 0.5(32 - 20) + 10 X 144 + 10(/ - 32) + 20it - 50) + 40 X 0.2415 
(t - 82) = 20 X 0.98 X 880.0 + 20(337.9 - t) 

60 + 1440 + lot - 320 + 20/ - 1000 + 9.7/ - 792 = 17,248 + 6758 - 20/ 



PROPERTIES OF STEAM 41 

59.5^ = 24,618 
t = 413.7°F. 

This result is of course absurd, as the temperature of the mixture cannot 
be higher than the temperature of the boiling point corresponding to the 
pressure at which the mixture takes place. Therefore, our assumption 
that all the steam is condensed must be wrong, and we know that part of 
it remains in the form of steam, and hence the temperature of the mixture 
is equal to the temperature of the boiling point corresponding to the pressure 
at which the substances are mixed. 

Then, substituting for t its value, and letting x represent the number of 
pounds of steam condensed, we have 

10 X 0.5(32 - 20) + 10 X 144 + 10(337.9 - 32) + 20(337.9 - 50) + 

40 X 0.2415(337.9 - 82) = 880.0a; 

60 + 1440 + 3059 + 5758 + 2472 = 88O.O3; 
880. 0.T = 12,789 

X = 14.53 pounds condensed. 

20 X 0.98 = 19.6 pounds = original weight of dry steam. 

Ans. 40 pounds air ] 

10 + 20 + (20 - 19.6) + 14.53 = 44.93 pounds water \ at 337.9°. 
19.6 — 14.53 = 5.07 pounds dry saturated steam J 

The difference between the results obtained in these two methods of work- 
ing this problem is due to the fact that in the first method we took account 
of the variation in the specific heat of water by using the heat of the liquid, 
h, from the tables, in place of {t — 32) wherever possible, while in the second 
method we assumed this specific heat to be constant and equal to 1. 

Example. — Find the resulting temperature and condition after mixing 10 
pounds of ice at 20°, 20 pounds of water at 50°, and 30 pounds of steam at 
100 pounds pressure and 400° temperature. Mixture takes place at 25 
pounds pressure. 

First Method 



Solution. — 






10 X 0.5(32 - 20) 


60 




10 X 144 


= 1,440 




' 


1,500 B.t.u. 


= heat to raise ice to water at 32°. 


20 X (50 - 32) 


= 360 




30 X 0.53(400 - 337.9) 


= 987 




30 X 1188.8 


= 35,664 






37,013 B.t.u. 


= heat given up by water and 
steam. 




1,500 





35,513 B.t.u. = heat available. 
60 X 235.6 = 14,136 B.t.u. = heat to raise water to 266.8^ 



21,377 B.t.u. = heat available to evaporate 
water. 



42 HEATING AND VENTILATION 

21 377 

goo f; = 22.89 pounds steam. 

Ans. 37.11 pounds water j ^^ ^gg gop 

22.89 pounds dry saturated steam / 

Second Method 

Assume the steam to be all condensed and let the temperature of the 
mixture be t°. Then 

10 X 0.5(32 - 20) + 10 X 144 + 10(1 - 32) + 20{t - 50) = 30 X 0.53 

(400 - 337.9) + 30 X 880.0 + 30(337.9 - t) 

60 + 1440 + 10^ - 320 + 20t - 1000 = 987 + 26,400 + 10,137 - SOt 

60t = 37,344 

t = 622.4° I 

This result is, of course, impossible and we see at once that only part of 
the steam is condensed, and that the temperature of the mixture must be that 
of the boiling point corresponding to the pressure at which the mixture | 

takes place. ■■ 

This problem differs from the previous ones in that the pressure of the I 

mixture is different from the original steam pressure, and we must proceed 
in a slightly different manner. 

Assume for the moment that the steam has all been condensed and that j 

we have 60 pounds of water at 622. 4°F. Then assume that the temperature j 

of the water is dropped to the temperature of the boiling point (266.8°) j 

corresponding to the pressure (25 pounds) at which the mixture is made. ■ 

Each pound will give up, approximately (622.4 — 266.8) B.t.u. This heat 
can then be used to re-evaporate part of the water. Therefore, since the i 

latent heat corresponding to 25 pounds is 933.6, we have 1 

60(622.4 - 266.8) 60 X 355.6 21,330 ^^ ^^ , , . 

933:6 = "933:6~ = 933^ = ^2.85 pounds re-evaporated. 

i 

Ans. 37.15 pounds water 1 t 266 8°F * 

22.85 pounds dry saturated steam / ' ^ j 

Problems 

1. Required the temperature after mixing 3 pounds of water at 100°F., 

10 pounds of alcohol at 40°F., and 20 pounds of mercury at 60°F. ' 

2. Required the temperature and condition after mixing 5 pounds of ice * 
at 10°F. with 12 pounds of water at 60°F.i 

3. Required the temperature and condition after mixing 10 pounds of ice 
at 15°F. with 1 pound of water at 212°F. 

4. Required the temperature and condition of the mixture after mixing 
5 pounds of steam at 212°F. with 20 pounds of water at 60°F. 

6. One pound of ice^ at 32° is mixed with 10 pounds of water at 50° and 



1 Specific heat of ice equals 0.5. 

2 Latent heat of fusion of ice = 144 B.t.u. 's. 



PROPERTIES OF STEAM 43 

20 pounds of steam at 212°. What is the temperature and condition of the 
resulting mixture? 

6. Ten pounds of steam at 212° are mixed with 50 pounds of water at 
60° and 2 pounds of ice at 32°. What will be the resulting temperature and 
condition of the mixture? 

7. Ten pounds of steam at atmospheric pressure, 5 pounds of water at 
50° and 10 pounds of ice at 32° are mixed together, (a) What will be the 
resulting temperature of the mixture? (6) What will the condition of the 
mixture be? (c) If the steam is not all condensed, determine what per 
cent, of the steam will be condensed. 

8. Five pounds of steam at atmospheric pressure, 10 pounds of water at 
60°, and 2 pounds of ice at 20° are mixed at atmospheric pressure. What 
will be the resulting temperature? 

9. Ten pounds of ice at 10°, 20 pounds of water at 60° and 5 pounds of 
steam at atmospheric pressure are mixed at atmospheric pressure. Find 
the resulting temperature and condition of the mixture. 

10. Twenty pounds of steam at atmospheric pressure, 10 pounds of water 
at 60° and 50 pounds of air at 100° are mixed together at the pressure of the 
steam, (a) What will be the resulting temperature? (6) If the steam is 
not all condensed, determine what per cent, of the steam will be condensed. 

11. A mixture is made of 10 pounds of steam at atmospheric pressure, 
5 pounds of ice at 20°, 10 pounds of water at 50°, 30 pounds of air at 60°. 
(a) What will be the temperature of the resulting mixture? (6) What will 
be the percentages by weight of air, steam, and water in the mixture? 

12. What would be the resulting temperature and condition of a mixture 
of 10 pounds of water at 40°, 20 pounds of water at 60°, and 8 pounds of 
steam at 5 pounds pressure? Mixture takes place at 5 pounds pressure. 

13. Ten pounds of steam at 5 pounds pressure, 1 pound of ice at 32°, and 
20 pounds of water at 60° are mixed at 5 pounds pressure. What will be 
the temperature and condition of the resulting mixture? 

14. Five pounds of ice at 5°, 10 pounds of water at 50°, 20 pounds of air 
at 80°, and 5 pounds of steam at 20 pounds pressure are mixed at the pres- 
sure of the steam. Find the resulting temperature and condition of the 
mixture. 

15. Required the temperature and condition of the mixture after mixing 
10 pounds of steam at a pressure of 30 pounds absolute and a temperature 
of 250.3°F., 2 pounds of ice at 10°F., and 20 pounds of water at 40°F. Mix- 
ture takes place at the pressure of the steam. 

16. Fifty pounds of air at 100°, 10 pounds of steam at atmospheric pres- 
sure, and 10 pounds of water at 60° are mixed at atmospheric pressure. 
What is the temperature of the mixture and how much steam is condensed? 

17. Required the final temperature and condition after mixing at the 
pressure of the air 100 pounds of air at a temperature of 500° and a pressure 
of 100 pounds absolute, and 2 pounds of steam at 100 pounds absolute 
having a quality of 98 per cent. 

18. Five pounds of steam at 5 pounds gage pressure are mixed at atmos- 
pheric pressure with 10 pounds of water at 60°. What is the temperature 
and condition of the resulting mixture? 

19. Thirty pounds of water at 60°, 10 pounds of steam at 115 pounds 



44 



HEATING AND VENTILATION 



absolute and a temperature of 400°F., and 10 pounds of ice at 20° are mixed 
at atmospheric pressure. What will the resulting temperature be? What 
is the condition of the mixture? 

20. Ten pounds of ice at 20°F., 18 pounds of water at 80°, and 10 pounds 
steam at 75 pounds pressure and 90 per cent, quality, are mixed at atmos- 
pheric pressure. What is the resulting temperature and condition of the 
mixture? 

21. Two pounds of steam at 150 pounds absolute and a temperature of 
400°, 5 pounds of ice at 22°, and 10 pounds of water at 60° are mixed at 
atmospheric pressure. Find the final temperature and condition of mixture. 

22. Required the final temperature and condition after mixing at atmos- 
pheric pressure 3 pounds of ice at 22° and 3 pounds of steam at 100 pounds 
pressure and containing 2 per cent, moisture. 

23. Find the resulting temperature and condition of a mixture of 10 
pounds of steam at 150 pounds absolute and a temperature of 400°F., 10 
pounds of water at 60°F., and 50 pounds of air at 112°F. Mixture takes 
place at atmospheric pressure. 

24. Five pounds of ice at 0°, 20 pounds of water at 75°, and 15 pounds of 
steam at 50 pounds absolute and 95 per cent, quality are mixed at 20 pounds 
absolute. What is the resulting temperature and condition of the mixture? 

25. How many pounds of water will 10 pounds of dry steam heat from 
50° to 150° if the steam pressure is 100 pounds gage? 

26. If 10 pounds of steam at 100 pounds gage raised 93 pounds of water 
from 50° to 140°, what per cent, of moisture is in the steam, radiation being 
zero? 

27. A pound of steam and water occupies 3 cubic feet at 110 pounds 
absolute pressure. What is the quality of the steam? 



CHAPTER V 
RADIATORS 

39. Classification. — In a steam or hot-water heating system 
the conveying medium absorbs heat at the boiler and then 
flows to the radiators whose function is to transmit the heat to the 
air, walls, etc. of the room. There are several forms of radiation, 
the proper one to be used in any particular case depending upon 
the nature and use of the building. 

The selection of radiators of the proper size for each room in 
the building is very important. If the radiators are too small it 
will be impossible in the coldest weather to warm the building 
to the required temperature within a reasonable time, if at all. 
On the other hand, the installation of radiators of too large a 
size adds unnecessarily to the cost of the heating system, and 
tends to cause the rooms to be overheated during a large part of 
the time. In order to compute intelligently the amount of 
radiating surface required, it is necessary to study the various 
forms of radiation and the factors affecting the rate of heat 
transmission from each. 

Radiators may be divided into three classes: (a) direct ra- 
diators, (b) indirect radiators, and (c) semi-indirect radiators. 
Direct radiators, as explained in Chapter III, are located in the 
rooms to be heated, while indirect radiators are located elsewhere 
and a current of air conveys the heat from them to the rooms. 
Semi-indirect radiators are a combination of the other two forms, 
the radiators being installed in the rooms but delivering a large 
proportion of their heat output by means of a current of air 
which passes through them. 

40. Direct Cast-iron Radiators. — Direct radiators are made 
of cast iron, pressed iron, and wrought iron or steel pipe, the 
cast-iron radiator being by far the most widely used. It is 
composed of several sections cast separately and assembled, the 
number of sections being fixed by the amount of surface required. 
The sections are made in several different widths and heights so 
that for a radiator of a given surface, a wide range of shapes and 

45 



46 



HEATING AND VENTILATION 



sizes is available. The wider sections are divided through most 
of their length by vertical slots into from two to six segments or 





Single Column 
Radiator 



Two Column 
Radiator 



Three Column 
Radiator 



i 




Four Column Radiator 



Fig. 8 




Window Type 



"columns." The standard heights vary from 15 to 45 inches 
but the 38-inch height is the one most often used. In Fig. 8 are 



RADIATORS 



47 



shown several forms of cast-iron radiators. Radiators are fin- 
ished in several designs to harmonize with room decorations. 

In general appearance the form of radiator used for steam is 
quite similar to that used for water. The two designs are funda- 
mentally different, however, in that the sections of the steam 
radiator are joined together at the bottom only, while those in a 
hot-water radiator are connected at both top and bottom. Hot- 
water radiation may be used for steam but steam radiation could 
not be satisfactorily used in a hot-water system because air 
would become trapped in the top of each of the sections, pre- 
venting the water from filling them. 





Fig. 9. — Methods of assembling cast-iron radiators. 



The sections are joined by means of nipples. One method is 
to use a smooth tapered ''push nipple," fitting into tapered holes 
in the adjacent sections. Draw-bolts extending the full length of 
the radiator are used to force the joints to a tight fit. Another 
method is to use nipples threaded with ''right and left " threads. 
These nipples are cast with internal lugs and are turned up by 
means of a special wrench. The two methods of assembling 
are shown in Fig. 9. 

Cast-iron radiators are usually given a hydraulic pressure test 
at the factory of about 120 pounds per square inch. They are 
therefore suitable for working pressures approaching this figure 
but are seldom subjected to any such pressure except in the case 
of hot-water systems in tall buildings where the hydrostatic 



48 



HEATING AND VENTILATION 



head is high. The weight of cast-iron radiators averages about 7 
pounds per square foot of surface and the internal volume is about 
30 cubic inches per square foot of surface. This internal volume 
is largely fixed by the requirements of manufacture, the only stipu- 
lation from an engineering standpoint being that the passages 
must not be so small as to restrict the flow of the water or steam. 
Cast-iron radiation is also furnished in the form of ''wall 
radiators" as illustrated in Fig. 10. This type of radiation is so 




Fig. 10. — Wall radiator. 

proportioned that it takes up very little lateral space and is 
intended to be hung from brackets. It is well adapted for use 
in factory buildings. 

The rated external surface of radiators of various widths and 
heights is given in Table XI in square feet of surface per section. 

Table XI. — Heating Surface per Section — Cast-iron Radiation 



Height, 


One- 


Two- 


Three- 


Four- 


Six-column or 


inches 


column 


column 


column 


column 


"window" pattern 


45 




5 


6 


10 




38 


3 


4 


5 


8 




32 


2y2 


^Vs 


43^ 


6>^ 




26 


2 


2% 


3M 


5 




23 


1% 


23^ 








22 




2M 


3 


4 




20 


13^ 


2 






5 


18 






2K 


3 




16 








. . . 


m 


15 




13^ 








14 










. . . 


13 










3 



RADIATORS 49 

Wall Radiators 

Size of section, Heating surface, 

inches (approx.) square feet 

14 by 16 5 

14 by 22 7 

14 by 29 9 

It should be noted that the height of a radiator is taken as the 
total height above the floor for radiators having legs of standard 
height. The rated surface given in the table does not correspond 
exactly with the actual surface, but the difference may be neg- 
lected as the heat transmission from radiators is usually given 
in terms of rated surface. 

41. Radiator Tappings. — The end sections of cast-iron radia- 
tors are usually tapped for a 2-inch pipe thread and furnished 
with bushings having openings whose size depends on the size of 
the radiator. The sizes of the reduced openings for radiators 
intended for use with different systems of piping are as follows : 

Table XII. — Radiator Tappings 
Single-pipe Work 

Size of radiator, square feet Inches 

Up to 24 1 

24 to 60 IH 

60 to 100 m 

Above 100 2 

Two-pipe Work, supply and return 
Up to 48 1 by H 

48 to 96 IH by 1 

Above 96 VA by IK 

Water radiators, supply and return 
Up to 40 1 by 1 

40 to 72 IM by 1^ 

Above 72 li^ by IH 

For vapor systems supply, ^i inch, return, A inch. Air valve tapping, 
}4 inch on all radiators. 

42. Pressed-metal Radiators. — In recent years radiators 
made of pressed metal have been introduced and are now some- 
times used. Fig. 11 illustrates the appearance of one design of 
this form of radiator, and Fig. 12 is a cross-section. The sections 
are made of two sheets of metal pressed to shape and welded at 
the edges. In other designs the joint is a lapped seam. A 
special alloy- or soft steel selected for its non-corroding qualities 
is used. The radiator is assembled by welding the sectors 



50 



HEATING AND VENTILATION 



together or by joining them with lapped seams. Pressed-metal 
radiators are made in a variety of sizes corresponding to those 
of cast-iron radiation. The sections are very narrow and occupy 
much less space than do cast-iron radiators of equal surface. 
The weight per square foot of surface is also much less than that 
of cast-iron radiation, averaging about 2 pounds. The cost is 
about the same as that of ordinary cast-iron radiation. The 
radiating surface of pressed-metal sections of various heights and 
widths is given in Table XIII. Because of its hght weight this 



1 Welded 





I 



Fig. 11. — Pressed metal 
radiator. 



Fig. 12. — Section of pressed 
metal radiator. 



form of radiation is especially suitable for hanging on wall 
brackets. 

Table XIII. — Pressed-metal Radiation, Square Feet of Surface 

PER Section 





Width of section, inches 


Height of radiator, inches 






4M 


SH 


45 




6 


38 


3 


5 


32 


2y2 


43^ 


26 


2 


m 


22 


m 


3 


18 


IH 


2H 


14 


1 





43. Pipe Radiation. — In factories and other industrial buildings 
radiators built of pipe are often used and are a very satisfactory 



RADIATORS 



51 



form of radiation. These pipe coils usually consist of a pair of 
cast-iron headers connected by four or more pipes of either 1 inch 
or 13^ inches diameter. Pipe coils are usually made in the 
mitre form as shown in Fig. 13. The vertical lengths of pipe 
provide sufficient flexibihty to allow the longer horizontal 
members to expand freely. Some such provision is essential. 
The openings in one of the headers or the elbows are tapped 




Fig. 13. — Mitre pipe coil. 

with a left-hand thread so that the coil can be readily assem- 
bled. Pipe coils of the form shown in Fig. 14 are also some- 
times used, especially in hot-water work. 

Radiators were formerly made of vertical pipes screwed into 
a cast-iron base. This form of radiation is little used at present. 

44. Heat Transmission from Radiators.— Heat flows from the 
water or steam in a radiator into and through the metal wall 




Fig. 14. — Continuous pipe coil. 



and is transmitted from the outer surface partly by radiation 
and partly by convection. The resistance to heat flow offered 
by the walls of the radiator is so shght that the temperature of 
the outer surface is practically the same as that of the water or 
steam. It is very difficult to measure accurately the portions of 
the total amount of heat which are transmitted by radiation and 
by convection. Rough tests, however, indicate that about one- 
half of the total amount is given off in each manner. The total 




52 HEATING AND VENTILATION 

amount of heat transmitted per square foot of radiating surface 
is affected by several factors, such as the temperature difference 
between the radiating surface and the surrounding air, the nature 
of the surface, the height and shape of the radiator, and the 
location of the radiator in the room. 

45. Effect of Shape of Surface. — The form or shape of the 
radiator has a marked effect on the heat transmission, affecting 
both the amount radiated and that given off by convection. A 
greater amount of heat per square foot of surface is given off by 
radiation from a pipe coil or a single-column radiator than from 
a radiator of a wider pattern. This can be clearly understood 
from a study of Fig. 15 which represents horizontal cross-sections 

of a single-column and a three- 
column radiator. 

The rays of heat from points 
on the single-column radiator 
can travel in nearly any direction 
without interruption, while the 
rays emanating from many 
points such as A, on the surface 
^ ,^ of the inner columns of the 

Fig. 15. , , ,. ^ 

three-column radiator, are 
largely intercepted by the other portions of the radiator. 

The transmission of heat by convection is dependent upon the 
difference in temperature between the surface of the radiator and 
the air. The upper part of a radiator will transmit less heat per 
square foot by convection than will the lower part because of the 
increase in the temperature of the air as it ascends along the 
surface. Hence the average heat transmission per square foot 
is greater for short than for tall radiators, and for the same 
reason a radiator or pipe coil laid on its side will give off more 
heat than when in a vertical position. 

46. Effect of Painting. — The effect of the decorative painting 
on the heat transmission is sometimes considerable. Experi- 
ments made at the University of Michigan indicate that (a) if 
several paints of different kinds are applied successively the 
effect on the heat transmission is due entirely to the final coat, 
and (6) the aluminum or bronze paints have the greatest effect, 
reducing the heat transmission almost 25 per cent, in some cases. 
The relative effect of different kinds of paints is given in Table 
XIV. 




RADIATORS 



53 



-Relative Effect of Radiator Paints 



Relative 
transmission 



Table XIV 

Kind of paint ] 

Bare iron surface 1 . 000 

Copper bronze . 760 

Aluminum bronze . 752 

Snow-white enamel 1 . 010 

No-luster green enamel . 956 

Terra-cotta enamel 1 . 038 

Maroon glass Japan . 997 

White lead paint 0.987 

White zinc paint 1 . 010 

47. Coefficients of Heat Transmission. — The amount of heat 
transmitted from a radiator may be represented by the expression, 

2.0 



1.9 



1.8 



1.7 



1.6 



■51.5 



1.4 



1.3 



\ 






















^ 


















^ 






^""-^ 


Column 
















^-^ 


Column 


-- 




\ 




^ 






""^^ 


Column 


^ 














""^^ 


Column 


^ 


















^ 





20 



24 



28 



48 



Fig. 16. 



30 36 40 44 

Height of Radiator - Inches 
-Coefficient of heat transmission from radiators. 



H = SKits - tr) in which 

S = the area of the radiating surface in square feet. 
K = the coefficient of heat transmission in B.t.u. per square 
foot per hour per degree difference between radiator and 
room temperature. 
^3 = temperature of the steam or water in the radiator. 
tr = room temperature. 

The values of K, the coefficient of heat transmission for 
ordinary cast-iron radiation of various heights and widths, is 
given by the curves in Fig. 16 which are based on the results of 



54 



HEATING AND VENTILATION 



recent experiments. For other forms of radiation the values of 
K given in Table XV may be taken as average figures. 

Table XV. — Coefficient of Heat Transmission from Radiators 



B.t.u. per square foot 
per hour per degree 
difference in temperature 
Cast iron, height 38 inches: 

One-column 1 . 75 

Two-column 1 . 65 

Three-column 1 . 55 

Four-column 1 . 45 

Wall Coil: 

Heating surface 5 square feet, long side vertical 1 . 92 

Heating surface 5 square feet, long side horizontal 2.11 

Heating surface 7 square feet, long side vertical 1 .70 

Heating surface 7 square feet, long side horizontal 1 . 92 

Heating surface 9 square feet, long side vertical 1 . 77, 

Heating surface 9 square feet, long side horizontal 1 . 98 

Pi-pe Coil: 

Single horizontal pipe 2 . 65 

Single vertical pipe 2 . 55 

Pipe coil 4 pipes high 2 . 48 

Pipe coil 6 pipes high 2 . 30 

Pipe coil 9 pipes high 2.12 

This data is based on a temperature difference between the 
radiator and the air of about 150° which represents ordinary 
conditions. The rate of heat transmission increases slightly 
with an increase in the temperature difference. In Table XVI 
are given the results of a test on a 38-inch two-column radiator 

Table XVL — Coefficient of Heat Transmission for Varying Tem- 
perature Difference Between the Radiator and Room 



Difference in temperature, 
degrees 



80 
100 
120 
140 
150 
160 
170 
180 
190 



Coefficient of heat 

transmission, 

K 




.560 




580 




615 




645 




650 




675 




690 




705 




720 



} 



RADIATORS 



55 



showing this change in the value of K with an increasing tempera- 
ture difference. 

For ordinary conditions, that is, when the system is to be 
designed for a steam pressure of from 1 to 5 pounds and the room 
temperature is 70° or thereabouts, there will be no necessity for 
considering the change in the heat transmission with varying 
temperature differences. Occasionally, however, there are 



,u 



40 
700 

60 

I 20 
.SCOO 
S 80 

o 

':4o 



(2 60 

I 20 
3400 



■M300 
fo 
■3 60 

20 
200 

























^ 






\ 










'^ 




.^ 


•" 






1 
1 




..\^ 


pZ- 


>^ 


^ 


Roo 


nTe 


mp. 








1 
1 


\ c 
1 / 


P 


r.^ 


to^' 
















I 

1 . 


A 


^^- 






















\ 






















7 
























1 






















; 


ll 






















ll 
il 


1 






















ll 
ll 
1 


' 




\ 


















In 

ij 1 


; 






















ll ' 
1 1 


/ 


\ 




















1 


/ 


\ 




^c 


ond< 


nsal 


ion- 










1 
/ 


/ 




K 


K 






Ca 


3t II 


on 






/ 


/ 






>^ 


'»^ 


~ ~ 


























5 










( 


> 




/ / 












P 


resst 


d Ir 


on 






1 / 
1 / 
























1 / 
/ / 

























5.00 



10 20 30 40 50 

Time 
Fig. 17. — Result of a comparative test of a cast iron and a 



74 
72 
70 
68 
66 
64 S 



60 g 



.9.00 
pressed iron radiato. 



conditions such as in drying rooms and similar places that are to 
be kept at a very high temperature where it will make an appreci- 
able difference in the amount of radiation required. In some 
vacuum systems, also, where a very high vacuum is to be carried 
even in the coldest weather, it is desirable to take this factor 
into consideration. 

The heat transmission from pressed-metal radiation is practi- 
cally the same as that from cast iron. This is illustrated in Fig. 



56 



HEATING AND VENTILATION 



17 which shows the results of a test^ to determine the relative 
performance of the two forms of radiation under the same condi- 
tions. A radiator of each kind was placed in either of two 
similar rooms and the condension formed in each radiator was 
weighed at 10-minute intervals and the room temperatures were 
measured. While the rate at which the room was warmed was 
nearly the same in both cases it will be noted that in the case of 
the cast-iron radiator the initial condensation of steam is con- 
siderably greater. 

48. The Location of Radiators. — The location of the radiators 
is of considerable importance from several standpoints. Unless 




Effect of locating radiator beneath window. 



there are columns or other permanent structures in the interior 
of the room, it is necessary, at the outset, to place the radiators 
around the walls. The piping is also simplified by placing the 
radiators near the walls. If the radiators are placed against 
an interior wall there is a tendency for uncomfortable draughts 
to be formed by the cooling effect of the windows and outer wall 
tending to form a downdraught on one side of the room, together 
with the effect of the upward movement created by the radiator 
on the other side. If the radiator is placed under the window, 

^ See "Coefficient of Heat Transmission in a Pressed-Metal Radiator" 
by John R. Allen, Trans. A. S. H. & V. E., 1914. 



RADIATORS 57 

the current of air rising from the radiator will counteract this 
tendency and will produce an air movement as illustrated in Fig. 
18. The downward current caused by the cooling effect of the 
window causes a secondary circulation of the air between the 
radiator and the window. The location of the radiators beneath 
the windows if possible is, on the whole, the most desirable. 
Recent tests ^ have indicated that the transmission of heat is 
slightly greater when the radiators are located in other positions, 
but the slight gain in effectiveness is greatly overbalanced by the 
other considerations noted above. 

Radiators are often located under seats and shelves or behind 
grilles of various designs, the object being either to conceal 
the radiator or to conserve space. The heat transmission from 
the radiator is usually decreased by such enclosures, because of 
the restriction imposed on the circulation of the air through 
the radiator. Where it is necessary to place a radiator in such a 
location, an addition of from 10 to 30 per cent, should be made to 
its heating surface according to the degree to which the circula- 
tion is retarded by the enclosure. 

49. Proportioning Radiation. — The heat loss from the various 
rooms of a building having been calculated by the methods 
given in Chapter II, it is then necessary to determine the 
amount of radiating surface which will be required to supply 
the heat losses. It is necessary first to know the temperature 
of the steam or water in the radiator. If steam is the heat carry- 
ing medium the temperature will be that corresponding to the 
pressure to be carried. In many heating systems it is possible to 
carry a pressure of at least 5 pounds when necessary and for 
such systems the radiation is commonly figured on the basis 
of this pressure. If, however, special conditions require that a 
lower pressure be used the temperature of the steam which is 
assumed should be that corresponding to the pressure. Some 
types of vapor heating systems are designed to operate at nearly 
atmospheric pressure, and the radiation is consequently figured 
for 212°. If hot water is used the temperature will range between 
160° and 200°. The factors affecting the temperatures carried 
in hot-water systems will be discussed later. 

The type of radiation and the height must next be selected from 

* See report of Committee on Best Position of a Radiator, • Trans. A. S. H. 
& V. E., 1916. 



58 



HEATING AND VENTILATION 



a consideration of the nature of the building and of the space 
available. From the chart in Fig. 16 or from Table XV the 
heat transmission per square foot of surface for the type of ra- 
diation selected can be found and the total surface necessary to 
transmit the heat required can then be computed. For example, 
consider that the room shown in Fig. 7, page 23, is to be heated 
by a heating system which is to operate at a pressure of 2 pounds. 
The heat loss from the room was found by the B.t.u. method 
to be 8696 B.t.u. per hour with room temperature 70°. Assume 
that 38-inch, two-column radiation is to be used. The tempera- 
ture of steam at 2 pounds pressure is 218.2 and the difference in 
temperature between the steam and the air is 218.2° — 70° 
or 148.2°. From the chart in Fig. 16 we see that the value of K 
for 38-inch, two-column radiation is 1.65. For a temperature 
difference of 148.2° the heat transmission would be 244 B.t.u. 
per square foot per hour. Dividing 8696 by this figure we find 
that 35,6 square feet of radiation would be required. Since 
38-inch,' two-column radiation contains 4 square feet of surface 
per section, a radiator of nine sections would be used. 

50. Approximate Rules for Calculating Radiation. — The 
method outlined above should be followed when accurate results 
are necessary or when the conditions are exceptional. For 
rough calculations the average rate of heat transmission per 
degree difference in temperature per hour may be assumed to 
be 1 .65 B.t.u. If the steam pressure is assumed to be 5 pounds the 
temperature will be 227° and the temperature difference be- 
tween the radiator and the room, assuming the room temper- 
ature at 70°, would be 157°. The heat transmission per square 
foot of radiation per hour would then be 1.65 X 157 = 259 B.t.u. 

Having computed the heat loss by either of the methods given 
in Chapter II the radiation required can be approximately 
determined by dividing the computed heat loss by 259. 

51. Checking a Contractor's Guarantee. — The case often 
arises in which a contractor has guaranteed that the heating 
system as installed is capable of heating the building to 70° in 
zero weather and it is desired to prove that this is true 
without waiting for extremely cold weather. By means of the 
following method it is possible to determine the temperature 
to which the building must be heated in the warmer weather 
if the heating system is capable of heating it to the guaranteed 
temperature in the coldest weather. 



RADIATORS 59 

Let ti = temperature of outside air under contract conditions, 
usually 0°. 

^2 = temperature of air in building under contract con- 
ditions. 

tz = temperature of steam in radiator at pressure specified. 
Test made with steam at same pressure. 

ti = temperature of outside air during test. 

U = inside temperature to be maintained during test 
if system fulfills guarantee. 

h = computed heat loss from building per degree dif- 
ference in temperature. 

The heat loss from the building under conditions specified 
in guarantee would be 

h(t2 - to (1) 

The heat loss from the building under test conditions is 

h{t, - to (2) 

The heat loss from the radiators under contract conditions 
would be 

K{tz - t2) (3) 

in which K is the coefficient of heat transmission from the 
radiator. The heat transmission from the radiator under test 
conditions is 

K{t^ - to (4) 

Then the quantity (1) must be equal to the quantity (3) and 
the quantity (2) must be equal to (4), hence 
^ K{t3 - to 



{t2 - to 
and 



(5) 



Equating the right-hand members of equations (5) and (6), 
we have 

^3 — ^2 ts — ^5 



^2 ~~ ^1 ^5 ~ ^4 



(7) 



Assuming ti = 0°, ^2 = 70°, and ^3 = 228°, the temperature 
corresponding to 5 pounds steam pressure, and solving for t^ 
we have 

ts = 0.695^4 + 70 (8) 



60 



HEATING AND VENTILATION 



The following table has been computed from equation (8) and 
shows the room temperature, for different outside temperatures 
existing during the test, which must be maintained to fulfill 
a guarantee which specifies the temperatures and steam pressure 
given above. For other conditions equation (7) must be solved 
for ^5. 



Table XVII. — Room Temperature for Various Outside Temperatures 


Outside temperature 
during test 


Room temperature, 
two-column radiation 


Room temperature, 
three-column radiation 


-30 


52.0 


53.0 


-20 


58.0 


59.0 


-10 


64 


64.0 





70.0 


70.0 


10 


77.5 


75.0 


20 


83.0 


83.0 


30 


90.0 


89.0 


40 


97.0 


95.0 


50 


103.5 


105.5 


60 


110.0 


108.0 


70 


117.0 


115.0 


80 


123.5 


121.5 


90 


130.0 


128.0 


100 


137.0 


134.5 



52. Indirect Radiators. — Indirect radiators are so named be- 
cause they are located outside of the room to be heated and 
the heat is conveyed from the radiator to the room by a 
current of air. Indirect radiators are of two classes: gravity 
indirects, in which the circulation of the air over the radiating 
surface is produced by the difference in weight of the heated and 
unheated columns of air, and fan coils, over which the air is 
forced by a fan. Only the former will be considered here, 
the various types of fan systems being discussed in Chaptei- XV. 

There are two reasons for the use of gravity indirect radiators. 
Their chief advantage is that they can be arranged to introduce 
fresh air from outside and they are therefore desirable from a 
standpoint of ventilation. Another advantage is that the radia- 
tors are out of sight, which is desirable in any room or apartment 
where appearance is an important factor. It is seldom that 
indirect radiators are installed throughout an entire building 
because of the increased cost both of installation and operation 
as compared with direct radiation. In a residence, indirect 



RADIATORS 



61 



radiation is often installed in the living rooms where ventilation 
is most desired and where the appearance of the radiators would 
be objectionable, and direct radiation is used in the bed- 
rooms, halls, etc. The increased operating cost where indirect 
radiation is used is due to the fact that the large quantities of 
air which are brought in from outside must be heated up to room 
temperature or above. 

53. Forms of Indirect Radiation. — As indirect radiators are 
concealed, their appearance is not an important factor and they 
are therefore designed and installed from a standpoint of effect- 
iveness rather than appearance. • Since the resistance to heat 
transmission between the outer surface of the radiator and the 
air is greater than that from the steam or water to the inside 
surface of the radiator wall, it is desirable to make the external 




Fig. 19a. Fig. 19b. 

Forms of indirect radiators. 



surface of greater area than the internal. This is accomplished 
by adding projections in the form of pins or fins. Two forms of 
indirect radiation are illustrated in Figs. 19a and 196. The 
sections are joined together in the same manner as are the 
sections of direct radiators. The form shown in Fig. 196 is of 
the so-called short-pin type. A similar form having longer pins 
can also be obtained. 

54. Arrangement of Indirect Radiators. — Two common arrange- 
ments for indirect radiators taking air from outside are illus- 
trated in Fig. 20 and Fig. 21. The radiator is placed in a chamber 
or box usually situated in the basement of the building, as close 
as possible to the base of the flue leading to the room to be heated. 
The air is admitted to the radiator chamber by a duct or flue from 



62 



HEATING AND VENTILATION 



an opening in the outside wall or from the room above. This 
duet should be provided with a suitable damper, arranged if 




Cold Air 



Damper 
Control 
Cable - 



Warm Air 



M 



oooooooooooooooooooooo 
)00000000 oooooooooooooc 
oooooooooooooooooooooo 

JOOOOOOOOOOOOOOOOOOOOOC 
OOOOOOOOOOOOODOOOOOOOO 
)00000000 OOOOOOOOOOOOOC 
OOOOOOOOOOOOOOOOOOOOOO 
JOOOOOOOOOOOOOOOOOOOOOC 
OOOOOOOOOOOOOOOOOOOOO 

)Ooooooooooooooooooooc 
oooooooooooooooo 



^} 



oo oo o o 
:)0 oo o o 
oo oo oo 

DO OOO O 

oo O O O o 

DOO oo O 
O O GOO O 
DOO O O O 
> OO OOO 
O OOOO 
OOOO o o 



M 



To 
Room 



Mixing 
Damper 



Cleanout 



■% 



By Pass for 
Cold Air 



Fig. 20. — Indirect radiator with bypass. 

possible to close when the steam or water supply to the radiator 
is shut off. A bypass damper should also be provided, with a 

means of controlling it from 
the room, so that the tem- 
perature of the air can be 
readily adjusted. 

The casing surrounding in- 
direct radiators is usually built 
of galvanized iron and it should 
be bolted together with stove 
bolts, so that the sections can 
be easily removed. A much 
better method of construction, 
though a more expensive one, 
is to enclose the radiator in a 
brick chamber of sufficient 
size to permit access to the 
radiator. 

The duct leading from an 
indirect radiator should be 
carried to the room as directly 
as possible. Long horizontal pipes should be avoided. 
1 From "Pipe-fitting Charts" by W. G. Snow. 




FiQ. 21. — Indirect radiator. ^ 



RADIATORS 



63 



The indirect radiators are usually suspended in the box or 
chamber on iron pipes supported by rods from the joists. There 
should be at least 10 inches clearance between the radiator and 
the bottom and top of the casing, but the sides of the casing should 
fit the radiator as closely as possible, so that all of the air must 
pass through the radiator. Indirect radiators should be placed 
at least 2 feet above the water line of the boiler if they are to be 
operated on a gravity steam system, and should be so arranged 
that the condension will drain from them by gravity. The 
tappings of these radiators are the same as for two-pipe direct 
steam radiators. The following table gives the size of flues 
required for indirect radiators of various sizes. 

Table XVIII. — Size of Flues fob Indirect Radiators 



Heating 

surface, 

square feet 


Area of cold- 
air supply, 
square inches 


Area of hot- 
air supply, ' 
square inches 


Size of brick 
flue for hot 
air, inches 


Size of 

register, 

inches 


20 


30 


40 


8X8 


8X8 


30 


45 


60 


8 X 12 


8 X 12 


40 


60 


80 


8 X 12 


10 X 12 


50 


75 


100 


12 X 12 


10 X 15 


60 


90 


120 


12 X 12 


12 X 15 


80 


120 


160 


12 X 16 


14 X 18 


100 


150 


200 


12 X 20 


16 X20 


120 


180 


240 


14 X20 


16 X24 


140 


210 


280 


16 X 20 


20 X24 



Indirect radiators are sometimes arranged to re-circulate the 
air from the room instead of drawing in fresh air from outside. 
No ventilation is obtained by such an arrangement and the only 
advantage of the indirect radiator so installed is that it is 
concealed. 

55. Heat Transmission from Indirect Radiators. — Heat is 
transmitted from indirect radiators almost entirely by convec- 
tion. The amount of heat which will be transmitted from a 
given indirect radiator depends upon the temperature of the 
entering air, the temperature of the radiator, and the quantity of 
air passing through the radiator. The last quantity depends 
in turn upon the relative temperatures of the heated air and the 
unheated air, and upon the friction in the air ducts. In Fig. 
22 let h' be the average vertical distance from the radiator to the 



64 



HEATING AND VENTILATION 



point of delivery to the room. The force effective in producing 
the flow of air is then 

p = h' (Di - D2) 
in which Di = density of outside air. 

Z>2 = density of heated air. 

During a state of constant flow the quantity of air passing 
through the radiator will always be just sufficient so that the 
friction loss due to the air passing through the system will 
equal the available head producing flow. Owing to the impossi- 
bihty of determining in advance the resistance of the duct, 
because of lack of a standard type of construction, it is very diffi- 
cult to compute accurately the quantity of air which will pass 




Fig. 22. 

through the system. The action is also complicated by the stack 
effect of the heated room above. Accordingly the methods used 
in designing indirect radiators are based on experimental data. 
Table XIX gives the amount of heat transmitted from standard 
and long-pin radiators under various conditions. 

It will be noted that the temperature to which the air is heated 
by the long-pin radiator is less than that to which it is heated by 
the short-pin radiator with the same quantity of air passing. 
This is undoubtedly due to the fact that the pins are so long that 
the rapid removal of heat by the air causes the ends to become 
cooled. The long-pin type, however, is very desirable for use 
when large quantities of air are required, as the air passages are 
ample. This is the work for which it is primarily designed. The ' 



RADIATORS 



65 



short-pin type gives better results for ordinary residences and 
other buildings where only small quantities of air pass through 
the radiator. 

Table XIX. — Heat Transmission from Pin Radiators 



Cubic feet 

of air passing 

per square foot 

of radiation 

per hour 


Rise in temperature 
of the air 


Pounds of steam 

condensed per square 

foot of radiation 


B.t.u. transmitted per 

square foot of radiation 

per degree difference in 

temperature between 

steam and air 


Standard 
pin 


Long pin 


Standard 
pin 


Long pin 


Standard 
pin 


Long pin 


50 
75 
100 
125 
150 
175 
200 
225 
250 
275 
300 


147 
143 
140 
138 
135 
132 
130 
127 
123 
121 
119 


140 
137 
135 
132 
129 
126 
123 
120 
118 
115 
112 


0.125 
0.170 
0.240 
0.295 
0.355 
0.410 
0.470 
0.530 
0.585 
0.645 
0.700 


0.150 
0.210 
0.260 
0.310 
0.360 
0.405 
0.450 
0.490 
0.530 
0.570 
0.610 


0.80 
1.17 
1.51 

1.85 
2.22 
2.57 
2.90 
3.25 
3.60 
3.90 
4.22 


0.95 
1.27 
1.60 
1.90 
2.20 
2.47 
2.72 
3.00 
3.20 
3.40 
3.60 



56. Calculation of Indirect Radiation. — In order to determine 
the required size of an indirect radiator it is necessary to assume 
the quantity of air that will pass through the radiator. In school 
buildings and other buildings where a large air supply is desired 
and where the flues will be of ample size, the amount of air passing 
per square foot of radiation may be assumed to be 200 cubic feet 
per hour. In residences and buildings where the flues are 
usually small, the amount of air passing per square foot of surface 
per hour does not exceed 150 cubic feet. The air should be 
assumed to enter the radiator at the minimum outside tempera- 
ture for which the system is to be designed. If this temperature 
is 0°, for example, and the quantity of air passing is taken as 
200 cubic feet per hour per square foot of radiation, the air will 
be heated according to figures given in Table XIX to about 130°. 
The air which enters the room at this temperature gives up its 
heat to supply the heat lost by conduction through the walls, 
and finally finds its way out of the room through the window 
cracks, foul air flues, etc. Each cubic foot of air, therefore, 
gives up enough heat to lower its temperature from 130° to 70°, 



66 HEATING AND VENTILATION 

if the latter is the room temperature. This amount of heat is 
equal to 

(130^- 70) ^ 200 = 218 B.t.u. per square foot of 

radiator surface. 

This amount is available for supplying the heat losses through 
the walls and the amount of surface in the indirect radiator 
for the case given above would be equal to the computed heat 
loss through the walls divided by 218. 

57. Approximate Rules for Indirect Heating. — The following 
approximate rules may be used to compute the amount of indirect 
heating surface required. This quantity in each case is desig- 
nated by R. 

Rule 1. — For ordinary rooms: 

R = I 27 ^ glass surface) X 0.6 

For entrance halls: 

R = I J + glass surface) X 0.75 

Rule 2. — Figure the heating surface the same as for direct 
heating and add 40 per cent. 

Rule 3. — For rooms on first floor: 

„ volume of room, cubic feet 
^= 40 

For second and third floor rooms : 

o volume of room, cubic feet 
^= 50 

For stores and large rooms : 

o volume of room, cubic feet 
^= 60 

58. Combination of Direct and Indirect Radiators. — A very 
common arrangement is to install enough indirect radiation to 
give the proper amount of air for ventilation and to install direct 
radiation to supply the heat losses. The direct radiation would 
then be computed in the ordinary manner, as if there were no 
other source of heat. This system has the advantage of being 
more economical, as less cold air need be heated per hour. 



RADIATORS 



67 



Further, when the rooms are unoccupied, the indirect radiators 
may be entirely shut off, resulting in a considerable saving of 
fuel. 

59. Semi-direct Radiators. — When only a small quantity of 
air is needed for ventilation semi-indirect or ^'flue" radiators 
may be used in place of indirect radiators. A radiator of this 
form is shown in Fig. 23. The air enters through a grating in the 
wall behind the radiator and passes into a metal box which en- 
closes the lower part of the radiator and thence up through the 
spaces between the sections. 
Dampers in the fresh air open- 
ing and in the base may be ad- 
justed to allow part or all of 
the air to re-circulate from the 
room. Radiators used for this 
purpose are of a special design, 
the sections being so shaped 
that the passages between them 
are divided into a number of 
vertical flues. A test recently 
conducted on a flue radiator 
showed that about 45 per cent, 
of the ttoal heat transmitted 
is carried off by the air passing 
through the flues, the remaining 
55 per cent, being given off by 
radiation and by convection 
from the outer surfaces. When 
flue radiators are used the 
amount of surface allowed 
should be about 25 per cent, 
greater than if direct radiation were 




Flue radiator. 



used. 



Problems. 

1 To be properly heated, a certain building requires 5627 square feet of 
30-incli, one-column radiation. How much would be required if wall coil, 
of sections containing 9 square feet of surface, long side horizontal, were 
used? How much would be required if pipe coils, 9 pipes high, were used? 

2. A heating system is guaranteed to heat a building to 70° in zero 
weather at 5 pounds pressure. A test is made with the outside tempera- 
ture at 10". What inside temperature must be reached to fulfill the 
guarantee? 



68 HEATING AND VENTILATION 

3. A heating system is guaranteed to heat a building to 65° with the 
outside temperature at 10° and at a steam pressure of 1 pound. A test is 
made with the outside temperature at 15°. What inside temperature must 
be maintained to fulfill the guarantee? 

4. Assume that the room in Fig. 7, p. 23, is to be heated by indirect 
radiation. Inside temperature 70°, outside temperature 0°. How much 
radiation would be required and what would be the proper size for the 
flues and registers? 

5. Take the same room as in Prob. 4 and figure the amount of indirect 
radiation required by each of the approximate rules in Par. 57. 

6. Take the same room as in Prob. 4 and figure the amount of in- 
direct radiation required if the inside temperature is 65° and the outside 
temperature 10°. 



, CHAPTER VI , 
STEAM BOILERS 

60. Fuel. — Before taking up the subject of boilers, it is desir- 
able to study the various kinds of fuel and the general principles 
of combustion. 

Coal, coke, wood, oil, and gas are used as boiler fuels. Coal 
is by far the most widely used fuel in the United States, being 
found in varying amounts in no less than thirty States in the 
Union. It is of vegetable origin, being thie remains of vegetation 
which existed during a former geological period and which gradu- 
ally reached its present state through the action of decay and of 
earth pressure. The chief constituents of coal are carbon, 
hydrogen, oxygen and nitrogen. The carbon exists partly in an 
uncombined or ''fixed" state and partly in combination with the 
hydrogen and oxygen as hydrocarbon compounds which are 
given off as gases when the coal is heated. Coals are classified 
as anthracite, bituminous, etc., according to the relative pro- 
portions of fixed carbon and volatile matter as given in Table XX. 



Table XX. — Classification of Coals 



Kind of coal 



Composition per pound 
of combustible 



Volatile 
matter 



Fixed 
carbon 



Calorific 

value per pound 

of combustible 



Anthracite 

Semi-anthracite 

Semi-bituminous 

Bituminous — Eastern . 
Bituminous — Western 



3.0- 7.5 

7.5-12.5 

12.5-25.0 

25.0-40.0 

35.0-40.0 



97.0-92.5 
92.5-87.5 
87 . 5-75 . 
75.0-60.0 
65.0-50.0 



14,900-15,300 
15,300-15,600 
15,600-15,900 
15,800-14,800 
15,200-13,700 



All coals contain more or less non-combustible matter, con- 
sisting principally of moisture and ash. The nitrogen in the 
coal is also a non-combustible but it is customary to treat it as 
combustible matter. The moisture content of different coals 
varies from 2 per cent, to as much as 20 per cent, and the ash 
content from 4 to 20 per cent, by weight of the coal as mined. 

69 



70 



HEATING AND VENTILATION 



It will be noted that the percentages in Table XX are based on 
1 pound of combustible. 

The bituminous and semi-bituminous coals are the most 
abundant and are the kinds used for most- industrial purposes. 
Many bituminous coals are of the variety known as ''caking" 
coals because, when heated, the lumps fuse together into a solid 
crust, while the so-called ''non-caking" or free-burning coals do 
not possess this quality. Bituminous coals burn with a char- 
acteristic yellow fiame and emit smoke unless burned under 
favorable conditions. They are sold in the sizes given in Table 
XXI and as " run-of-mine " or ungraded. 





Table XXI. — Coaimercial Sizes of Bituminous Coal 


Kind of coal 


Will pass through 
bars spaced 


Will not pass through 
bars spaced 


Lump 




\yi inches 
^^ inch 


Nut . . - 




\}/i inches 
^i inch 


Slack 



< 



The slack coal does not command as high a price as the larger 
sizes because of its higher ash content and the difficulty of 
burning it. 

Anthracite or hard coal is principally used for domestic pur- 
poses and for other conditions where a smokeless coal is required. 
It ignites slowly but burns steadily with a short blue flame. It 
is of relatively great density and does not crumble easily. It 
is marketed in the sizes given in Table XXII. 



Table XXII. — Commercial Sizes of Anthracite Coal 



Kind of coal 



Will pass through 



Will not pass through 



Rice 

Buckwheat 

Pea 

Chestnut 

Stove or range 

Egg 

Large egg 



3^-in. mesh 

3^ -in. mesh 

3^-in. mesh 

1^-in. mesh 

1%-in. mesh 

23^-in. mesh 

4-in. mesh 



^-in. mesh 

3^ -in. mesh 

3^ -in. mesh 

%-in. mesh 

lyi-in. mesh 

1^-in. mesh 

2%-in. mesh 



61. Composition and Analysis of Coal. — Coal consists of carbon, 
hydrogen, sulphur, oxygen, and nitrogen combined in various 



STEAM BOILERS 71 

ways, together with moisture and ash. The moisture includes 
both that originally contained in the coal and that added during 
storage and shipment. The moisture content of a given coal is 
determined by subjecting a finely powdered sample to a tempera- 
ture of about 220°F. for about 1 hour and noting the loss in weight 
during that time. This method, while not giving an absolutely 
accurate result, is the one universally employed. 

The amount of volatile matter is determined by subjecting 
a sample of dried coal to a high temperature out of contact with 
air until there is no further loss of weight, and noting the de- 
crease in weight. The residue left after distilling off the volatile 
matter consists of the fixed carbon and ash. By burning the 
sample in an uncovered crucible the fixed carbon can be removed , 
leaving the ash. 

There are two forms of coal analysis — the ''Proximate Analy- 
sis" and the ^' Ultimate Analysis." The former consists of a deter- 
mination of the moisture, volatile matter, fixed carbon, and ash in 
the manner just described. This is the more useful form of 
analysis and is the one generally used by engineers. The ulti- 
mate analysis, which consists of a determination of the carbon, 
hydrogen, oxygen, nitrogen, and sulphur, is usually made in a 
chemical laboratory. In the proximate analysis, the percentages 
may be reckoned either on a basis of dry coal or coal ^'as received." 
In the former case the moisture content is given in addition. 

The heat value or calorific value of a fuel is the amount of heat 
developed by its combustion, expressed in B.t.u. per pound of 
fuel. The heat value of coal is determined by igniting a sample 
of known weight in a closed vessel surrounded by water and 
noting the rise in temperature of the water. From the pre- 
viously determined thermal capacity of the vessel and water the 
heat developed can be computed. The calorific value of the 
various kinds of coal was given in Table XX. 

62. Coke. — Coke is the residue left after the volatile matter is 
driven off from bituminous coal and consists mainly of carbon. 
It is produced as a byproduct in the manufacture of artificial 
gas and is also manufactured for various industrial purposes. 
It is of relatively low density and is consumed rapidly so that 
when used as a boiler fuel frequent firing is required unless a very 
deep bed of fire is maintained. 

63. Combustion. — Combustion may be defined as the chemical 
combination of a substance with oxygen which proceeds at such 



72 HEATING AND VENTILATION 

a rate that a high temperature is produced. Carbon is the 
principle combustible in coal. When its combustion is complete, 
it forms carbon dioxide (CO2); when it is incomplete it forms 
carbon monoxide (CO). The hydrogen in the coal unites with 
oxygen to form water vapor and the nitrogen, which is an inert 
substance, is set free. For economy in fuel consumption it is 
necessary that combustion be complete and to this end the supply 
of air must be ample. In order to insure a sufficient supply to all 
parts of the fuel bed, it is necessary to supply from 150 to 300 per 
cent, of the theoretical requirements. As all of this excess air 
leaves the boiler at the flue-gas temperature, it is evident that 
in the interest of economy the amount of excess air used should 
be reduced to the minimum required for complete combustion. 
The best index of the amount of excess air in the percentage of 
CO2 in the flue gases. If exactly enough air is supplied the 
CO2 content, by volume, of the flue gases would be 21 per cent. 
In practice, however, the best results are obtained with a CO2 
content of from 10 to 15 per cent., the higher figure being attain- 
able only with mechanical stokers. In the ordinary hand-fired 
furnaces of heating boilers the CO2 content of the flue gases 
ranges between 5 and 13 per cent. 

64. Smoke. — Smoke consists principally of unburned carbon in 
finely divided particles set free by the splitting up of unburned 
hydrocarbon gases. While the waste represented by the visible 
products themselves is not great, smoke is an indication of incom- 
plete combustion and consequently of wasted fuel. A great deal 
of damage is caused annually by smoke and in most communities 
the making of excessive smoke is prohibited by law. 

Smoke may be avoided by the use of anthracite coal, coke, 
or the semi-bituminous coals, which have little volatile matter, 
and by insuring complete combustion when coals high in volatile ' 

matter are used. When coal containing much volatile matter is j 

placed on a hot bed of fuel, the volatile matter is distilled off. 
In order that complete combustion of this gas may take place, 
sufficient air must be supplied and intimately mixed with the 
combustible gases. Furthermore, the combustion space must ^ 

be of sufficient size so that combustion can be completed before ' 

the gases come into contact with the relatively cold surfaces 
of the boiler. The air supply must not be so copious or at such 
a low temperature as to chill the mixture below the temperature 
required for combustion. These requirements are met by the 



STEAM BOILERS 73 

use of various appliances and of furnaces of special design which 
will be discussed later. 

65. Comparison of Different Fuels. — It might be reasonably 
assumed that from the standpoint of economy that coal is the 
most desirable which has the greatest calorific value per dollar 
of cost. This is not strictly true, however, as there are other 
factors which affect the actual economy. Moisture in the coal 
is undesirable, principally because of the fact that it absorbs 
heat when the coal is burned and passes up the stack as super- 
heated steam. An excessive amount of ash is objectionable be- 
cause the cost of its transportation from the mine must be 
paid and because of the trouble which it causes in the furnace. 
It obstructs the passage of air through the fuel bed and fuses 
together into clinkers which must be broken up and removed 
from the furnace. The formation of clinker is the most trouble- 
some when the ash is fusible at a comparatively low temperature 
and also is thought to be aided by the presence of sulphur. The 
latter should therefore not exceed d}^ per cent. 

Coals high in volatile matter are undesirable unless the fur- 
nace is designed to burn them, for reasons which have been 
previously stated. For the smaller sizes of coal and for coals 
which cake heavily a greater draft is necessary and if not avail- 
able the desired rate of combustion may be impossible of attain- 
ment. In general, the smaller sizes of coal cost less per heat 
unit because of the less demand for them. When purchased in 
large quantities the price of coal is often based upon the calorific 
value and ash content. This is a very desirable way to purchase 
coal. 

Where smokeless combustion is desirable or compulsory, an- 
thracite coal is perhaps the most suitable fuel. The facts that 
it is the cleanest coal to handle and that it requires little atten- 
tion render it especially desirable for domestic use. Coke is a 
very good fuel when the firepot of the boiler is of sufficient 
depth to hold a large quantity of it. Otherwise, a good fire 
cannot be maintained without more frequent attention than can 
conveniently be given. Semi-bituminous coals, such as '' Poca- 
hontas" and ''New River" are capable of being burned in an 
ordinary furnace with little smoke because of the small amount 
of volatile matter which they contain. 

The bituminous coals contain the greatest heat value per unit 
of cost, but have some marked disadvantages. Bituminous coal 



74 HEATING AND VENTILATION 

is particularly dirty to handle, which is a strong argument 
against its use in residences. It is also difficult to burn it with- 
out smoke except in furnaces of special design, intelligently and 
carefully operated. With the increasing cost of coal and growing 
scarcity of anthracite, it is becoming more widely used, however, 
in all classes of work and many special furnaces are being 
developed for it. 

66. Boilers. — Strictly speaking, a boiler is a vessel in which 
steam is generated by the application of heat. The furnace 
in which the heat is developed is often practically an integral ■ 
part of the boiler, however, and the term ''boiler" therefore often 
refers to the combination of boiler and furnace. The primary 
requirement in a boiler is that it be of sufficient strength to 
withstand the pressure which is to be carried in it. In boilers 
used for heating purposes only, this is comparatively simple 
as the pressure carried rarely exceeds 10 pounds. Secondly, 

the heating surface must be sufficient in proportion to the grate i 

surface so that the heat will be largely removed from the flue | 

gases before they leave the boiler; and the boiler should be so * 

designed that the flue gases are made to impinge upon and rub 
along the heating surfaces to the greatest possible extent as this 
''scrubbing" action increases the rate of heat transfer. The 
boiler must be so designed that the water may circulate freely 
to the heating surfaces and the steam pass away from them 
without restriction. Also, the area of the surface of the water 
must be sufficient so that the bubbles of steam rising through the 
water can escape without excessively disturbing the water level. j 

If the liberating surface is restricted or if the steam space is too ♦ 

small, there is a tendency for priming (i.e., the carrying of water 
into the steam pipes) to take place, particularly when the boiler 
is being forced. This consideration is more important in a low- 
pressure boiler than in a high-pressure boiler as the bubbles of 
steam have a greater volume at the lower pressure. In boilers 
used for heating purposes, it is desirable to have a large storage 
of water so that steam will be continuously generated in spite of 
slight variations in the condition of the fire. A very large volume 
of water is not desirable, however, when the boiler is operated 
intermittently as the entire mass of water must be heated when- 
ever the boiler is put into service. 

67. Types of Boilers. — The most common type of boiler for 
heating residences and small buildings is the round cast-iron 






STEAM BOILERS 



75 



boiler shown in Fig. 24. This type of boiler consists of from three 
to five main castings such sls A, B, and C (Fig. 24). The castings 
are joined by the tapered nipples iV", N, and are drawn and held 
together by vertical bolts. For a boiler of a given diameter, 
the amount of heating surface can be varied by the size or number 
of the intermediate sections such as B in the figure. It is reason- 
able to suppose that the ''taller" boilers are somewhat the more 
efficient since the ratio of heating surface to grate area is the 
greater. Round boilers may be obtained having rated capacities 
up to about 1600 square feet of radiation. 




Fig. 24. — Round cast-iron boiler. 



Fig. 25. — Sectional cast-iron boiler. 



The ''sectional" boiler, as shown in Fig. 25 is obtainable in 
rated capacities up to about 9000 square feet of radiation. It 
consists of from five to ten sections joined with nipples. In the 
larger sizes the sections are made in halves, the idea being to 
make the boiler capable of being easily transported and erected. 
One of the advantages of sectional boilers is the possibility of 
erecting them in an existing building without the necessity of 
cutting holes in the floor or walls. 

Steel boilers are frequently used for heating, particularly in 
large buildings. A common type is the return-tubular boiler 
illustrated in Fig. 26. The return-tubular boiler (so named 



76 



HEATING AND VENTILATION 



because the gases flow through the flues toward the front of the 
boiler) is desirable for heating purposes because of its large 
water storage, ample circulating areas, and large liberating 



Damper 



«jn^ Gallows 
I r^ Frame 




Fig. 26. — Horizontal return-tubular boiler. 

surface. Another type of horizontal fire-tube boiler is the firebox 
boiler shown in Fig. 27. Boilers of this type in which the furnace 
is incorporated with the boiler are known as portable boilers as 



3^^:te^ 




Fig. 27. — Firebox boiler. 

distinguished from brick-set boilers of which that in Fig. 26 is an 
example. 

Steel boilers of the return-tubular and firebox types are suitable 
for working pressures up to 100 pounds. The marine-type 
boiler shown in Fig. 28 can be used for higher pressures as the 
fire does not touch the outer shell. Water-tube boilers, in which 



STEAM BOILERS 



77 



the water circulates through the tubes and the flue gases over the 
outside of them, are used for capacities of over 150 horsepower 
and for high-pressure work. 



Uptake 




-Marine-type boiler. 

68. Grates. — For heating boilers the grates are usually of the 
shaking type, consisting of a number of toothed bars as shown 
in Fig. 29, having a bearing at either end and connected to a 
rocking link. The free area through the grate is about 50 per 
cent, of the gross area and the width of the openings varies from 
/'fe to }i inch, depending upon the size of fuel to be used. In 
large steel boilers the grates 
are often stationary and 
the ashes are removed 




Shaking grate bar. 



through the firing door. 

69. The Downdraft 
Boiler. — Owing to the 
difficulty of burning bituminous coal without smoke in the ordinary 
boiler, many boilers have been designed with special furnaces for 
this purpose, chief among which is the downdraft boiler illustrated 
in Fig. 30. The furnace consists of two separate grates placed 
one above the other. Coal is fed to the upper grate only and the 
air, instead of passing upward through the fuel bed as in the ordi- 
nary furnace, enters at the top and passes downward through it. 
Combustion is most active at the bottom of the fuel bed, and to 
prevent it from being burned out, the grate is made of hollow bars 



78 



HEATING AND VENTILATION 



through which the water in the boiler circulates. The volatile 
matter is freed from the coal on the top of the fuel bed and passes 
down through the incandescent fuel where most of it is ignited. 
The lower grate contains an incandescent fuel bed consisting of 
small pieces of coke from which the gases have been driven and 
which have fallen down through the bars of the upper grate. In 
the hot combustion chamber between the grates the gases de- 
scending from the upper fuel bed mingle with the hot air which 
enters through the lower grate and complete and smokeless com- 
bustion takes place. 

In addition to the important feature of burning any grade of 
coal without smoke and with complete combustion of the volatile 




Fig. 30. — Sectional downdraft boiler. 

matter, the downdraft furnace has other advantages. No 
trouble is experienced from clinkers, if the boiler is properly- 
fired, and the performance is uniform as there are no cleaning 
periods to disturb the fuel bed. 

In firing a downdraft furnace, it is important that the main 
fuel bed be not seriously disturbed. It should be frequently 
sliced, but just sufficiently to crack the caked mass of fuel so 
that air can find its way through it. No green coal should ever 
be fed to the lower grate; it should contain only such material 
as falls through from the upper grate. The main air supply of 
course enters through the firing door of the upper grate and the 
fire is controlled by the regulation of this air opening. The one 



STEAM BOILERS 



79 



great disadvantage of the downdraft furnace is the necessity for 
fairly careful firing, without which the smokeless feature is lost. 
If green coal is shovelled on the lower grate, if the lower grate is 
not properly covered, or if the upper fuel bed is violently dis- 
turbed by poking, much smoke will be formed. Any of these 
things are very liable to be done by a careless attendant. 

70. Other Special Furnaces. — Another means of promoting 
the thorough mixing and combustion of the air and volatile 
matter necessary for smokelessness is by the use of some form 
of brick ignition arch or wall. In the boiler shown in Fig. 31 the 
gases are made to pass from the fuel bed into the '^ mixing" 




Combustion 
Chamber 
Mixing Chamber 

Fig. 31. — Smokeless boiler with brick ignition wall. 

chamber and thence through the vertical slot in the ignition wall 
to the combustion chamber. The ignition wall becomes highly 
heated and serves to assist in the ignition of the gases, the narrow 
slot causing a thorough intermingling of the gases and air. The 
air supply enters principally through the fuel bed and an auxiliary 
air supply is provided above the fuel bed. 

With a boiler of this type, some smoke is unavoidable during the 
firing periods when the doors are open, admitting great volumes 
of cold air and when the green coal thrown upon the fire is giving 
off a large amount of hydrocarbon gases. For the greater part 
of the time, however, smokeless combustion is obtained. 



80 



HEATING AND VENTILATION 



Other devices for the prevention of smoke consist of ignition 
arches of various designs, and of steam jets directed into the 
furnace so as to cause a thorough mixing of the air and gases. 

An interesting type of special boiler which is coming into 
wider use is the magazine-feed type designed primarily for burn- 
ing the small sizes of anthracite coal and coke. These fuels 
cannot be burned successfully in an ordinary boiler because of 
the difficulty of getting air through a fuel bed of any considerable 
thickness, while a thin fuel bed requires very frequent firing. 




Fig. 32. — Magazine feed boiler. 



With the magazine feed such as illustrated in Fig. 32 the fresh fuel 
is fed by gravity as required and the fuel bed is at all times 
sufficiently thin to allow air to pass through it. The magazine 
holds sufficient fuel so that the boiler needs attention only at 
much less frequent intervals than does the ordinary boiler. 

71. Proportions of Boilers. — The heating surfaces in a boiler 
are defined as those surfaces which have water on one side and 
hot gases on the other side. In order that the boiler may be 
efficient the ratio of heating surface to grate surface should be 
large. The ratio is limited, however, by such factors as the cost 



STEAM BOILERS 81 

of the boiler and the friction introduced in the path of the flue 
gases. In small boilers it is usual to allow 1 square foot of grate 
surface to every 15 to 30 square feet of heating surface. For 
boilers of 50 horsepower and over, it is usual to allow from 30 to 
40 square feet of heating surface per square foot of grate surface, 
while in very large boilers the ratio is 50 or 60 to 1. Experience 
has shown that in small heating boilers it is advisable to allow each 
square foot of heating surface to evaporate only about 2 pounds 
of water per hour as a greater rate of steaming results in a high 
exit temperature of the flue gases. In large boilers the evapo- 
ration rate varies from 3 to 6 pounds per square foot of surface. 

Small heating boilers are distinctly different in operation from 
large power or heating boilers. In the latter, coal is being fed 
to the boiler almost continuously and the flues are carrying 
a large quantity of gases. Small heating boilers, on the other 
hand, are fed with coal only at infrequent intervals and very 
little of the heat is transmitted to the water by the flue surfaces, 
the greater part of the heat being transmitted by the fire surfaces, 
i.e., those which are in the paths of the heat rays emanating 
from the fuel bed. During the periods when the drafts are closed 
most of the steaming in the boiler is produced by the fire surface. 
It is good practice to have about 60 per cent, fire surface and 40 
per cent, flue surface in small cast-iron boilers. 

72. Boiler Rating. — The standard unit of boiler capacity is the 
boiler horsepower which is defined as the equivalent of 34.5 
pounds of steam evaporated ''from and at" 212° {i.e., from water 
at 212° into saturated steam at the same temperature). As each 
pound of steam so evaporated requires the transmission of 970.4 
B.t.u., the boiler horsepower is equivalent to 33,479 B.t.u. per 
hour. It is customary to allow 10 square feet of heating surface 
per boiler horsepower for establishing the rated capacity of a 
boiler. Most types of boilers have an overload capacity of from 
50 to 100 per cent. 

Heating boilers are not usually rated by horsepower, but 
upon the square feet of direct steam radiation which they will 
handle. It is never desirable to force a heating boiler up to its 
maximum capacity as this involves the maintaining of a rapid 
rate of combustion, necessitates frequent firing, and results in 
uneconomical operation because the exit temperature of the 
flue gases is high. The rating is based upon the amount of 
radiation which the boiler will supply when fired at certain 



82 



HEATING AND VENTILATION 



intervals (usually 8 hours) and with the assumption that the 
charge of fuel will be entirely consumed except for an amount 
necessary to kindle the fresh charge of coal. The rating of a 
heating boiler is therefore largely a function of the capacity of 
the firepot. 

In computing the load on a boiler, allowance should be made 
for the greater condensing power of indirect radiation and for 
the condensation taking place in the piping. Three square feet 
of covered pipe should be considered as being equivalent to 1 
square foot of uncovered pipe. If is advisable to be rather liberal 
in choosing the size of boiler and to allow some excess capacity 
over and above the total capacity actu- 
ally required. 

Some engineers install two boilers in 
buildings of considerable size, each having 
a capacity sufficient to take care of about 
two-thirds of the maximum load which 
could be expected. This practice enables 
one boiler to be operated at an active 
rate of combustion during the greater 
part of the time and provides a spare 
boiler sufficient to handle almost the en- 
tire load if forced. In very large build- 
ings even more spare capacity should 
be provided. 

73. Boiler Accessories. — Every steam 
boiler should be equipped with a safety 
valve of sufficient capacity to handle all 
of the steam which the boiler can generate. 
A safety valve of the spring-loaded type 
is shown in Fig. 33. A safety valve of 
the weight and lever type is undesirable as it can be rendered 
inoperative through the suspending of extra weights on the lever. 
The safety valve should be piped a few feet away from the boiler 
so that a discharge of steam from it will not injure the covering 
of the boiler. The valve should be set to operate at from 2 to 
5 pounds above the normal pressure. 

A water column is required to indicate the level of the water 
in the boiler. It should be equipped with a gage glass and with 
try-cocks as shown in Fig. 34, the latter being desirable for use 
in case the gage glass becomes broken or to verify its showing. 




Fig. 33.— Safety valve. 



STEAM BOILERS 



83 



A steam pressure gage similar to that in Fig. 35 is also required. 

'To facilitate the control of the drafts and to maintain an even 

steam pressure some form of damper regulator operated by the 

pressure in the boiler is very desirable. The form shown in 

Fig. 36 consists of a corrugated 
metal bellows which expands under 
pressure, closing the ashpit damper 
and opening the check damper in 
the flue by means of chains or rods 
connected to the lever. The pres- 
sure at which the action takes 





Fig. 34. — Water column. Fig. 35. — Steam pressure gage. 

place depends upon the location of the weight on the lever 



arm. 



74. Draft and Chimney Construction. — In order to maintain 
combustion in a furnace a continuous supply of air must be moved 




Fig. 36. — Damper regulator. 

through the fuel bed. In the ordinary heating boiler, the air 
is drawn through by means of a chimney, which also serves to 
dispose of the smoke and other products of combustion. The 
chimney produces a ''draft" or movement of the air because 
of the difference in weight between the column of hot gases in 



84 



HEATING AND VENTILATION 



the chimney and the cold outside air. The intensity of the force 
produced depends upon the average difference in temperature be- 
tween the hot gases in the stack and the outside air and upon the 
height of the stack. This force must be sufficient to move the 
required amount of air and gases through the boiler and stack 
against the frictional resistances interposed by the various 
obstructions. These resistances consist of (a) the resistance of 
the fuel bed, (6) the resistance of the flues of the boiler, (c) the 
resistance of the damper and breeching, and (d) the resistance 
of the stack itself. The first three items are fixed by the kind of 
fuel used and by the design of the boiler. The last item depends 
upon the height, cross-section, and construction of the stack. 
If the cross-sectional area of the stack is too small, the friction 
in the stack itself will be great and the sum of the various re- 
sistance factors may be greater than the available draft produced 
by the stack. Increasing the area of the stack results in a re- 
duction of its frictional resistance and therefore in an increase 
in the net amount of draft available at the foot of the stack for 
overcoming the boiler and breeching losses. Increasing the 
height of the stack obviously increases the available draft. 
Table XXIII. — Size of Chimney Flues 



Direct radiation 


Height of chimney flue (feet) 
Diameter of chimney flue (inches) 


Steam in 
square feet 


Water in 
square feet 


30 ft. 


40 ft. 


50 ft. 


60 ft. 


80 ft. 


250 

500 

750 

1,000 

1,500 

2,000 

3,000 

4,000 

5,000 

6,000 

7,000 

8,000 

9,000 

10,000 


375 

750 

1,150 

1,500 

2,250 

3,000 

4,500 

6,000 

7,500 

9,000 

10,500 

12,000 

13,500 

15,000 


7.0 
9.2 
10.8 
12.0 
14.4 
16.3 
18.5 
22.2 
24.6 
26.8 
28.8 
30.6 
32.4 
34.0 


6.7 
8.8 
10.2 
11.4 
13.4 
15.2 
18 2 
20.8 
23.0 
25.0 
27.0 
28.6 
30.4 
32.0 


6.4 
8.2 
9.6 
10.8 
12.8 
14.5 
17.2 
19.6 
21.6 
23.4 
25.5 
26.8 
28.4 
30.0 


6.2 
8.0 
9.3 
10.5 
12.4 
14.0 
16.6 
19.0 
21.0 
22.8 
24.4 
26.0 
27.4 
28.6 


6.0 
6.6 
8.8 
10.0 
11.5 
13.2 
15.8 
17.8 
19.4 
21.2 
23.0 
24.2 
25.6 
27.0 



The dimensions of a chimney can be computed from a consider- 
ation of the principles stated above, \ but for ordinary cases 
^ For methods of chimney design see Gebhardt, "Steam Power Plants." 



STEAM BOILERS 



85 



they can be determined by empirical rules. Table XXIII by 
Prof. R. C. Carpenter gives the dimensions of chimneys for 
various amounts of steam or water radiation. If the flue is 
square, the sides should be equal in length to the diameter for 
a round flue given in the table, it being assumed that the corners 
of a square flue are not effective. 

The available draft of such chimneys, as measured with an 
ordinary draft gage, should approximate the values given in 
Table XXIV. 

Table XXIV. — Draft in Small Chimneys^ 





Temperature of chimney gases, 


deg. F. 


Height in feet 


200 250 


300 




Draft — inches of water 


60 


0.27 


0.32 


0.35 


55 


0.25 


0.29 


0.32 


50 


0.23 


0.26 


0.29 


45 


0.21 


0.23 


0.26 


40 


0.18 


0.21 


0.23 


35 


0.16 


0.19 


0.20 


30 


0.14 


0.16 


0.17 


,25] 


0.12 


0.14 


0.14 


20 


0.09 


0.11 


0.12 



In measuring the available draft the gage should be connected 
to the breeching on the chimney side of the damper. The fire 
should be regulated so that the temperature of the stack gases 
will approximate working conditions and the damper should be 
quickly closed immediately before the reading is taken. 

A chimney must be so constructed that the wind, deflected by 
surrounding buildings, will not blow down into it and thus im- 
pede the draft. An illustration of two common sources of trouble 
is given in Fig. 37. The wind striking the sloping roof is de- 
flected over the peak and down into the chimney. The chimney 
should be extended well above the top of all adjacent buildings. 

The round flue is the most effective per square foot of area 
but is somewhat difficult to construct. For small buildings a 
square or rectangular flue is used. It should be lined with tile 
and should be smooth and free from leaks. Offsets should 
always be avoided, if possible, and when unavoidable should 

^ From "Chimneys: Their Design and Construction," by Harold L. Alt, 
Heating & Ventilating Magazine, March, 1917. 



86 



HEATING AND VENTILATION 



be made with gradual bends. No other openings of any sort 
should be made in the flue to which the boiler is connected. 

In large buildings the stack is often constructed of steel, 
lined with brick. 



T---i 




Fig. 37. — Effect of wind on chimneys of insufficient height. Dotted lines show 

proper construction. 



75. Hot-water Heaters. — For hot-water systems the heater 
used is very similar to the steam boiler. In cast-iron water 
heaters of both the round and sectional type a smaller casting is 
substituted for the steam dome. For large buildings ordinary 
steel boilers are often used, although in many cases the water is 
heated by the exhaust steam from generating units in some form 
of ''surface" heater. 

The water column, safety valve, and pressure gage are of course 
omitted from a water heater. 

PROBLEMS 



1. A boiler evaporates 1749 pounds of water per hour from a tempera- 
ture of 180° into steam at 10 pounds gage pressue and 98 per cent, quality. 
What is the equivalent evaporation "from and at" 212°, and what boiler 
horsepower is developed? 

2. A boiler containing 820 square feet of heating surface evaporates 2600 
pounds of water per hour, from a temperature of 190° into steam at 50 
pounds gage pressure and 97 per cent, quality. What per cent, of rating 
is developed? 



CHAPTER VII 
STEAM HEATING SYSTEMS 

76. Class'fication of Systems. — In a steam heating system the 
piping and radiators must be arranged with a view to perform- 
ing successfully three functions: (1) the conveying of steam to the 
radiators, (2) the removal of air from the radiators, and (3) the 
draining off of the condensation from the radiators. The many 
types of steam heating systems in use differ from one another 
mainly in the manner in which these operations are accomplished. 
It is the purpose of this chapter to discuss these various types 
and their relative merits for different classes of buildings. 

Steam heating systems may be divided roughly into two gen- 
eral classes according to the manner in which the connections 
are made to the radiators. In the single-pipe systems the steam 
is conveyed to the radiator through a pipe which enters the 
radiator at the bottom of one of the end sections. The con- 
densation which forms in the radiator flows back through this 
same pipe. In the two-pipe systems a separate system of piping 
is provided to carry away the condensation, and in some cases 
the air, from the radiators. 

77. Single-pipe System. — The simplest form of single-pipe 
system is that shown in Fig. 38. The nearly horizontal pipes 
leaving the boiler are called the steam mains. The vertical 
pipes extending to the upper floors are called risers. Steam is 
generated in the boiler and flows through the mains and risers 
into the radiators, forcing the air out ahead of it through some 
kind of an air valve on the end of the radiator opposite the sup- 
ply connection. In the system shown in Fig. 38 the condensation 
formed in the radiators drains down the risers into the mains and 
back to the boiler. The direction of the flow of the condensation 
is thus opposite to the direction of the steam flow. In the risers 
this is not objectionable if the system is small. In the mains, 
however, the water and steam flowing in opposite directions are 
very liable to interfere with each other, unless the mains are of 
such a diameter that the steam will travel at a very low velocity. 

87 



88 



HEATING AND VENTILATION 



If the pipes are small so that such interference takes place the 
water is picked up by the steam and driven to the end of the main 
with a characteristic loud cracking noise known as ''water- 
hammer." 

A better design of a single-pipe system is shown in Fig. 39. 
The main pitches away from the boiler and the condensation 





p 1 


pC' 


I t 


J 


1 


^— L_ 







C—) 



■C5 



Fig. 38. — Single-pipe system — mains pitching toward boiler. 



entering the main from the risers flows along with the steam. 
The main circles the basement and a drip connection carries the 
condensation from the end of it to the boiler, entering below the 
water-line. This is the most common form of single-pipe system. 



'3f 




G. 



^ 



Fig. 39. — Single-pipe system — mains pitching away from boiler . 

Another form of single-pipe system is the single-pipe re- 
lief system shown in Fig. 40. The connections to the risers 
are taken from the bottom of the main and a drip connec- 
tion is taken from the foot of each riser to a 'Vet" return main, 
so called because it is below the water line of the boiler. The 



STEAM HEATING SYSTEMS 



89 



advantage of this method is that no condensation from the radia- 
tors is carried by the main. It also has the advantage of allow- 
ing the main to be placed close to the basement ceiling, which is 
desirable if the basement is used for any purpose for which full 
head room is desired. This system is sometimes referred to as 
a two-pipe system because of its return main. It will be noted, 
however, that there is only one connection to each radiator, 
as in the other single-pipe systems. 

The single-pipe system is simple in design and can be installed 
at a low cost. It is especially suitable for residences and small 
buildings where a low-priced system is desired. In large build- 
ings, however, a single-pipe system is less desirable, on account of 
the large quantities of water which must be carried in the steam 



iO. 



Q Pf 



-{ZZI 



G. 



iQ 



iQ 



Fig. 40. — Single-pipe relief system. 



mains and risers. Another objection is the trouble which is 
sometimes experienced due to the radiators not draining properly. 
If the inlet valve is not closed tightly when the radiator is shut 
off, or if the valve leaks, some steam will continue to flow into 
the radiator and because of the small area of the opening it is 
impossible for the condensation to drain out against the inflowing 
steam. As a result the radiator becomes partly filled with water 
and when the valve is again opened an annoying cracking and 
pounding takes place as the water pours out against the inrushing 
steam. 

78. Two-pipe Systems. — Fig. 41 shows a typical two-pipe 
dry return system. As the term indicates, the return mains 
are above the water line of the boiler and are filled with steam. 
The supply mains and risers are installed and connections taken 
from them to each radiator in much the same manner as in the 



90 



HEATING AND VENTILATION 



single-pipe system. A '' return" connection is made from each 
radiator to the return main, through which the condensation 
from the radiator flows. As the steam has a free passage through 
the radiator from the supply main to the return main, it is evident 
that the latter will be filled with steam at a pressure approaching 
that in the supply mains, a slight pressure drop taking place 
through the radiator and its connections. The end of each 
supply main is dripped into the return main through a 4 or 5-foot 
seal as at b,b, which serves to prevent the full steam pressure from 
entering the return main. One of the chief faults of the two- 
pipe, dry return system is the tendency for the steam to enter 
the radiator through the return connection, especially if the 



Q 



a 



o 



tOt 



tES 



a 



£13 



Fig. 41. — Two-pipe dry return system. 

return valve is opened first when turning on the radiator, and 
thus trap air in the center of the radiator. 

In the ''wet return" system this trouble is eliminated. The 
return main is below the water line of the boiler and separate 
connections are made to it from each radiator and from the low 
points in the supply mains. A wet return system is shown in 
Fig. 42. 

It is evident that no steam can enter the radiator through the 
return connection, as the lower end of each connection is sealed 
with water. The water level in the return pipes is sometimes con- 
siderably higher than that in the boiler, as will be evident upon 
consideration of Fig. 42. If the pressure on the surface of the 
water in the boiler is the same as that on the surface of the water 
in the return lines, then the water levels will he the same. But 
if a pressure of 2 pounds, for example, exists in the boiler and 
there is a drop due to friction, of J^ pound along the main, then 
the water at (6) will rise to a height sufficient to balance the drop 



STEAM HEATING SYSTEMS 



91 



between the boiler and the point (6). It is necessary, therefore, 
to use pipes sufficiently large so that the pressure drop will not 
be excessive; and futhermore, no radiators should be located 
less than 2 feet above the water line of the boiler. The wet 
return system will usually operate with less noise than a dry 




Fig. 42. — Wet return system. 

return system as the condensation does not flow in horizontal 
pipes containing steam. A disadvantage of two-pipe systems is 
the cost of a double set of radiator valves, and the nuisance of 
having to operate both valves. Sometimes a check valve is used 
instead of a shutoff valve on the return end of the radiator. 



Bl 



St 



jQ_S_jQ 



S 



jR I P 



Fig. 43. — Overhead distribution — single-pipe system. 

79. Overhead System. — In buildings over three or four stories 
high the overhead system illustrated in Fig. 43 is nearly always 
used. The main circles the attic and risers extend down from 
it to the basement, supplying the radiators on the successive 



92 



HEATING AND VENTILATION 



floors. The steam is carried to the attic main by a main riser 
from which no radiators are supphed. The chief advantage of 
the overhead system of distribution Ues in the fact that the steam 
and condensation in the risers are both moving downward. 
Smaller risers can therefore be used without causing noise or 
interfering with the circulation of the system. The fact that 
the large piping is in the attic rather than the basement is also 
an advantage when the matter of head room and appearance in 
the basement is a consideration. 

The overhead method of distribution may be applied to either 
the single-pipe or two-pipe system. In the latter case, the return 
risers and the return main are arranged in the same manner as in 
the ordinary upfeed system. 

80. Air-line Systems. — In the systems previously described, 
the air is discharged from the radiators through some kind of an 
air valve to the atmosphere. In order to force the air out of the 
radiators the steam must be at some pressure above atmosphere, 
and thie temperature of the water in the boiler must be higher 
than 212°. Consequently, when the fire dies down or is banked 
at night, no steam is delivered to the radiators. Furthermore, 
when pressures only slightly above atmosphere exist in the boiler, 
the radiators near the boiler are wholly or partially filled with 
steam while those farthest from the boiler may be cold, resulting 
in an uneven heating of the building. Another objection to the 
ordinary means of air removal is the disagreeable odor of the air 
discharged and the noise and frequent leakage of steam and water 
which are characteristic of most ordinary air valves. 

To overcome these objections a system of air lines is sometimes 
provided to convey the air from all of the radiators to a pump or 
ejector located in the basement. In place of an ordinary air 
valve, an ''air-line valve" is used, having a pipe connection on 
the discharge side, and designed to allow air to pass through it 
but to close against steam. By the suction of the pump or ejector 
a partial vacuum is maintained in the air-line system and as 
the steam output of the boiler falls off the vacuum extends into 
the radiators, piping, and boiler. The boiling temperature is 
consequently reduced to the temperature corresponding to the 
existing pressure and the boiler continues to generate steam for a 
considerable time after the fire is banked. The circulation of the 
entire system is also improved and a more even heating is secured. 
In some cases no attempt is made to maintain a vacuum on the 



STEAM HEATING SYSTEMS 



93 



air lines and they are used only to eliminate the ordinary air- 
valve troubles. 

81. Vapor Systems. — A form of two-pipe system having many 
desirable features is the vapor system, which with shght modifica- 
tions is also variously termed ''vacuo-vapor/' ^'atmospheric," 
etc. These names are derived from the fact that such systems 
are intended to operate on pressures but little above, and in some 
cases below atmosphere. The essential features of vapor systems 
are: 

I. The use of radiators of the hot-water type with supply valve 
at the top and with return connection which carries off both the 
air and condensation. 

II. The use of a graduated supply valve by means of which the 
amount of steam admitted to the 

radiator can be controlled. 

III. Absence of steam in the return 
lines, which are either open to the 
atmosphere or under a pressure less 
than atmosphere. 

The arrangement of a radiator 
in a vapor system is shown in Fig. 
44. By means of a graduated 
supply valve the steam supply can 
be controlled so that only the 
amount required to heat the room 
is admitted to the radiator. The 
steam flows into the successive 
sections of the radiator at the top 
and fills them through part or all 
of their length, depending upon the 

degree of valve opening, in the manner shown in Fig. 44. The 
surface of the part of the radiator which is filled with steam is at 
nearly the steam temperature. The remainder of the surface is 
warmed by the condensation which trickles down the inside sur- 
faces, the temperature decreasing toward the bottom. The 
temperature of the discharged condensation is thus materially 
lowered and in cases where the condensation is not returned to 
the boilers this is an advantage from an economic standpoint. 

An important characteristic of vapor systems is that there is 
normally no steam in the return lines. They carry both the 
air and condensation from the radiators and are often open to 




Fig. 44.- 



-Radiator in a vapor 
system. 



94 



HEATING AND VENTILATION 



the atmosphere. The steam is prevented from flowing into the 
return hne from the radiators by either of two means: 

(a) By some device such as a trap or an orifice installed on the 
return end of the radiator. 

(6) By limiting the maximum area of opening of the inlet valve 
so that at no time will more steam be supplied to the radiator 
than can be condensed in it. 




Fig. 45c. 
Various forms of thermostatic traps. 



82. Radiator Traps. — In most vapor systems some kind of a 
trap is used. The most common is the thermostatic trap which 
is so constructed as to allow the comparatively cool air and 



STEAM HEATING SYSTEMS 



95 



condensation to pass but to close when the steam at higher 
temperatures reaches it. Several forms of thermostatic traps 
are illustrated in Figs. 45a, h, and c. All consist fundamentally 
of a thin-walled metal chamber A (Fig. 45c) containing a volatile 
liquid, such as alcohol, which vaporizes when heated and forms 
sufficient pressure inside the chamber, at a temperature of about 
210°, to expand it and bring the valve B against the seat C. In 
operation the trap remains open while air and condensation 
pass through it but when steam reaches it and heats the thermo- 
static element it closes, and remains closed until condensation 
accumulating in it cools a few degrees, causing it to open again 
and discharge the condensation. 



JIZE 



rzL 





By-pass 
Fig. 46. — Radiator trap of float type. 



Outlet 



Another type of radiator trap is the float trap in which the open- 
ing and closing of the valve is dependent entirely upon the flow 
of condensation into the trap. A common form is that illus- 
trated in Fig. 46. The valve A is normally closed against the 
seat B and the air from the radiator is discharged through the 
passage C in the center of the float. When condensation has 
accumulated to a sufficient height in the body of the trap, it 
raises the float D, opening the valve and allowing the condensa- 
tion to flow out until the normal level is reached. The chief objec- 
tion to float traps is that they are sometimes noisy in operation 
and are then a source of annoyance to the occupants of the room. 
Also, there is a tendency for some leakage of steam through the 
trap to take place. 



96 



HEATING AND VENTILATION 



Air 



Water 




Fig. 47. — Retarder. 



83. Retarders. — While the thermostatic and float traps are 
designed to close positively against the steam, another type of 
return fitting is used which only restricts its passage, allowing 
a small amount to pass into the return line when the radiator is 
filled with steam. This is not objectionable as the leakage is 
usually so sHght that it is condensed in the return lines. Retard- 
ers are usually in the form of an orifice as in Fig. 47. These 
fittings have the advantages of being of low cost, of simple 
construction, and of requiring no adjustment. For systems of 

moderate size they are quite satis- 
factory. If, however, the pressure 
regulation is such that a pressure 
of over a few ounces may exist in 
the system there is a possibility of 
an excessive amount of steam leak- 
ing into the return lines, which is 
very undesirable. Such fittings 
are often used in connection with 
a supply valve having a restricted opening such as those used in 
the atmospheric system described in the next paragraph. 

84. Atmospheric Systems. — The primary function of the 
return fittings previously described is to prevent or restrict the 
leakage of steam into the return line. In the so-called atmos- 
pheric system this is accomplished in another way — by restricting 
the supply so that there will be no uncondensed steam to overflow 
into the return line. In such systems no special return fitting 
is provided and the return line is connected direct to the radiator. 
The maximum area of opening of the supply valve when in its 
wide open position is restricted by means of an orifice disc, for 
example, so that with an assumed pressure in the supply pipe 
■ — usually about 5 ounces — only the amount of steam which the 
radiator will condense can enter it. It is evident that the 
amount of steam which will pass through the maximum opening 
of the supply valve will vary with the pressure in the supply pipe. 
Therefore any pressure less than that for which the system is 
designed will not cause sufficient steam to enter the radiator in the 
coldest weather. Any considerable increase in pressure above 
this amount will force more steam through the valve than the 
radiator will condense and the excess will enter the return piping. 
If the system has been carefully designed, so that at any one time 
nearly the same pressure exists at the supply connections of all the 



STEAM HEATING SYSTEMS 



97 



radiators, and if the pressure is closely regulated at the boiler, 
the atmospheric scheme is quite successful in systems of moderate 
size. 

When the water of condensation is not returned to the boiler, 
as often happens when steam is obtained from a central heating 
plant, it is always desirable to utilize the sensible heat in the 
condensation. Atmospheric systems accomplish this very effect- 
ively, the heat being removed as 
the condensation flows down the 
walls of a partly filled radiator and 
through the uncovered return pip- 
ing. In systems where the steam 
supply is restricted at the inlet 
valves the radiators are sometimes 
given from 10 to 20 per cent, more 
surface than is required, so that at 
no time will they be entirely filled and the lower portions are 
always available for removing the sensible heat of the condensa- 
tion. 

85. Supply Valves. — The supply valves of vapor systems are 
of two classes — those which limit and those which do not limit the 
amount of steam which can enter the radiator when the valve 
is in the wide open position. In Fig. 48 is shown a valve of the 




Fig. 48. — Supply valve — maximum 
opening not restricted. 



Fig. 




-Supply 



maximum opening restricted. 



second type. The full opening can be obtained by a half turn 
of the lever handle and the degree of opening is always readily 
discernible. The valve can be partly opened according to the 
amount of heat required. Fig. 49 shows one form of valve 

7 



98 



HEATING AND VENTILATION 



whose maximum opening may be restricted according to the 
size of the radiator on which it is to be used. The maximum 
movement of the handle is fixed by the stop (d) which is adjusted 
when the system is first put into service. 

86. General Arrangement of Vapor Systems. — The arrange- 
ment of the supply and return piping of a vapor system is shown 
in Fig. 50. The air is forced out of the radiators by the entering 
steam and passes through the return piping to the air vent located 
near the boiler. The supply main pitches away from the boiler 
and is dripped at the end by means of a trap similar to those used 
on the radiators or by a seal. 




Fig. 50. — Vapor system. 

87. Removal of Air from Return Piping. — Many different 
methods are employed for venting the air from the return piping. 
The simplest arrangement is to leave the return line open at all 
times to the atmosphere; but to provide against leakage of steam, 
in case of the failure of a radiator trap to close, a special vent 
valve is often provided which is normally open and closes only 
when steam reaches it. These vent valves are quite similar in 
principle to the ordinary thermostatic radiator trap. Float 
valves, or combination float and thermostatic valves, are fre- 
quently used, their function being to close when water reaches 
them and thus to guard against leakage in case of the accidental 
flooding of the return piping. 

Some vent valves include also a check-valve arrangement which 
allows air to escape from the system but prevents it from reenter- 
ing. The air is driven out of the system when the radiators and 
piping fill with steam; and as the steam output of the boiler de- 
creases, the pressure falls below atmosphere and the boiler con- 



STEAM HEATING SYSTEMS 99 

tinues to generate steam after the temperature of the water in it 
has dropped below 212°, as is the case in a vacuum system. 

88. Advantages of Vapor Systems. — It is apparent that for 
many classes of buildings vapor systems have some advantages 
over the other systems of heating, which may be summarized 
as follows : 

1. Control of the Heat Supply. — -This is accomplished by the 
manipulation of the supply valves and is therefore dependent 
for its effectiveness upon the attention of the occupants of the 
room. The improved design of inlet valve and its accessible 
location at the top of the radiator render it convenient to operate, 
but in many classes of buildings the occupants are not inclined 
to make use of this means of heat control. 

2. Circulation on Very Low Pressures. — This is of some ad- 
vantage from the standpoint of economj^, but is shared by the 
various kinds of vacuum systems. 

3. Noiseless Operation. — As the steam and water flow in sepa- 
rate systems of piping there is no opportunity for water-hammer. 

4. Discharge of Air into the Basement Instead of into the Rooms. — 
This eliminates the noise, smell, and drip which accompany the 
action of the ordinary air valve. 

5. Economy of Operation. — The opportunity afforded for accu- 
rate temperature regulation coupled with the possibility of cir- 
culation on very low pressures are productive of some economy. 
The measure of saving obtained, however, is rather uncertain. 

The disadvantages of vapor systems are the cost of the special 
fittings and appliances and the maintenance of the radiator traps. 

89. Vacuum Return Line Systems. — In a ''vacuum return 
line" system radiators of the hot water type maj^ be used, the 
arrangement being similar to that of a vapor system, or steam 
radiation can be used with the inlet valve at the bottom. In 
either case some form of trap is provided on the radiators and a 
vacuum pump is connected to the return main. 

Various kinds of "exhausters" have been devised for use on 
vacuum return systems but the most satisfactory apparatus is 
a simple pump. If a high-pressure steam supply is available, a 
steam-driven pump exhausting into the heating system is the 
most economical as regards the energy consumed, but motor- 
driven pumps have the advantage of requiring much less atten- 
tion and maintenance. A simple plunger pump is shown in 
Fig. 51. Pumps of this type can be built to operate on steam 



100 



HEATING AND VENTILATION 



pressures as low as 10 pounds but this necessitates a very large 
steam cylinder. In general, unless steam of at least 25 pounds 
pressure is available, it is better to use a motor-driven pump. 

For the proper operation of a vacuum system it is essential 
that the traps on the radiators be in good condition and close 
tightly. If they do not close tightly a leakage of steam into the 
return pipes will occur which will make it very difficult to main- 
tain the vacuum. A water spray at the vacuum pump suction 
is often used to condense any steam which may be present, but 
the use of an excessive amount of spray water is a source of 
considerable loss, as the spray water must necessarily be wasted, 
carrying with it the latent heat of the steam which it has 
condensed. 




Water 
Oyfinder 



Suction 



Fig. 51. — Steam-driven vacuum pump. 



One of the advantages of vacuum systems — the continued 
generation of steam at temperatures below 212°- — has already 
been brought out (Par. 80). Another important advantage is 
the better circulation in both supply and return pipes produced 
by the greater pressure differential. If, for example, a vacuum 
system is operated with a steam pressure of 2 pounds and a 
vacuum of 10 inches of mercury, the total differential is about 
7 pounds. A more rapid warming up of the system, better 
removal of air from the radiators, and better circulation in return 
lines having air or water pockets are other advantages which 
might be mentioned. In case some radiators are located, 
perforce, below the water line of the boiler a vacuum pump must 
be used to drain them properly. From the standpoint of 



STEAM HEATING SYSTEMS 101 

economy vacuum systems are of some advantage because of 
the lower radiator temperatures which exist if a vacuum is carried 
on the entire system at times when less heat is needed. When 
exhaust steam is used for heating a vacuum system permits of a 
lower back pressure on the engines and turbines and therefore 
tends to better the economy of the plant. Vacuum systems are 
best suited to large buildings where the advantages to be gained 
will justify the initial cost and the operating cost of the special 
equipment. 



CHAPTER VIII 
PIPE, FITTINGS, VALVES, AND ACCESSORIES 

90. Pipe. — The pipe used for the conveying of steam and water 
is made of either cast iron, wrought iron, or steel. Because of 
the low tensile strength of cast iron, pipe made of this material 
is suitable only for low pres ures, and must have a relatively 
thick wall. Owing to its ability to withstand corrosion it is 
especially adaptable for use where it must be buried in soil. 
Cast-iron pipe is seldom used in heating work. 

The pipe ordinarily used in heating and power plants is made 
from wrought iron or mild steel Steel pipe is much more widely 
used than wrought iron pipe at the present time being somewhat 
lower n price and for many purposes equally as desirable as 
wrought-iron pipe. The pipe commonly furnished to the pur- 
chaser under the name of wrought-iron pipe is likely to be steel 
pipe, so that if wrought-iron pipe is desired it must be clearly 
specified. It is rather difficult to distinguish between the 
two materials except by a chemical test. The threads cut 
upon steel pipe with an ordinary threading die are usually some- 
what the more ragged, however, and this affords a rough 
means of identification. Wrought-iron pipe is believed by 
many to be more resistant to corrosion than steel pipe, but 
the degree of superiority in this respect, if both kinds are well 
made, is problematical. 

In the manufacture of wrought pipe the strips of metal, cut to 
the proper width, are drawn through a bell to the cylindrical 
form and the edges welded together. In pipe of the smaller 
diameters a ''butt" weld is used and in the larger sizes a ''lap" 
weld. 

Wrought-iron and steel pipe are furnished in sizes ranging from 
J'^ inch to 30 inches nominal diameter. In the sizes up to 14 
inches the nominal diameters correspond approximately with 
the inside diameter of the pipe, while in the larger sizes the pipe 
is designated by its outside diameter. The nominal and actual 
dimensions of wrought-iron and steel pipe are given in Table 

102 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 103 

XXVI. Ordinarily it is not desirable to use the 3J^, 4}i, 7, 
9, and 11-inch sizes unless necessary, as these are regarded as 
odd sizes and their use is being gradually discontinued. For 
working pressures of over 150 pounds ''full-weight" pipe should 
be specified. Such pipe is selected as being of full card weight 
per running foot, while ordinary pipe varies somewhat from the 
standard weight because of slight variations in the thickness of 



Table XXVI. — Standard Wrought Steam, Gas and Water Pipe 
Table of Standard Dimensions 



Diameter 


Circum- 
ference 


Transverse 
areas 


Length 
of pipe 

per 
square 
foot of 
exter- 
nal 
surface 
feet 


Length 
of pipe 
contain- 
ing 1 
cubic 
foot, 
feet 


Nomi- 
nal 
weight 

foot, 
plain 
ends 




Nomi- 
nal 

inter- 
nal, 

inches 


Exter- 
nal, 
inches 


Ap- 

proxi- 
mate 
inter- 
nal 
diam., 
inches 


Exter- 
nal, 
inches 


Inter- 
nal, 
inches 


Exter- 
nal, 
square 
inches 


Inter- 
nal, 
square 
inches 


Number 

of 
threads 

per 
inch of 
screw 


H 


0.405 


0.269 


1.272 


0.845 


0.129 


0.057 


9.431 


2,533.775 


0.244 


27 


H 


0.540 


0.364 


1.696 


1.144 


0.229 


0.104 


7.073 


1,383.789 


0.424 


18 


?i 


0.675 


0.493 


2.121 


1.549 


0.358 


0.191 


5.658 


754.360 


0.567 


18 


Iri 


0.840 


0.622 


2.639 


1.954 


0.554 


0.304 


4.547 


473.906 


0.850 


14 


H 


1.050 


0.824 


3.299 


2.589 


0.866 


0.533 


3.637 


270.034 


1.130 


14 


1 


1.315 


1.049 


4.131 


3.296 


1.358 


0.864 


2.904 


166.618 


1.678 


11^/^ 


m 


1.660 


1.380 


5.215 


4.335 


2.164 


1.495 


2.301 


96.275 


2.272 


IIH 


m 


1.900 


1.610 


5.969 


5.058 


2.835 


2.036 


2.010 


70.733 


2.717 


IVA 


2 


2.375 


2.067 


7.461 


6.494 


4.430 


3.355 


1.608 


42.913 


3.652 


IIH 


2H 


2.875 


2.469 


9.032 


7.757 


6.492 


4.788 


1.328 


30.077 


5.793 


8 


3 


3.500 


3.068 


10.996 


9.638 


9.621 


7.393 


1.091 


19.479 


7.575 


8 


SH 


4.000 


3.548 


12.566 


11.146 


12.566 


9.886 


0.954 


14.565 


9.109 


8 


4 


4.500 


4.026 


14.137 


12.648 


15.904 


12.730 


0.848 


11.312 


10.790 


8 


4^^ 


5.000 


4.506 


15.708 


14.156 


19.635 


15.947 


0.763 


9.030 


12.538 


8 


5 


5.563 


5.047 


17.477 


15.856 


24.306 


20.006 


0.686 


7.198 


14.617 


8 


6 


6.625 


6.065 


20.813 


19.054 


34.472 


28.891 


0.576 


4.984 


18.974 


8 


7 


7.625 


7.023 


23.955 


22.063 


45.664 


38.738 


0.500 


3.717 


23.544 


8 


8 


8.625 


8.071 


27.096 


25.356 


58.426 


51.161 


0.442 


2.815 


24.696 


8 


8 


8.625 


7.981 


27.096 


25.073 


58.426 


50.027 


0.442 


2.878 


28.554 


8 


9 


9.625 


8.941 


30.238 


28.089 


72.760 


62.786 


0.396 


2.294 


33.907 


8 


10 


10.750 


10.192 


33.772 


32.019 


90.763 


81.585 


0.355 


1.765 


31.201 


8 


10 


10.750 


10.136 


33.772 


31.843 


90.763 


80.691 


0.355 


1.785 


34.240 


8 


10 


10.750 


10.020 


33.772 


31.479 


90.763 


78.855 


0.355 


1.826 


40.483 


8 


11 


11.750 


11.000 


36.914 


34.558 


108.434 


95.033 


0.325 


1.515 


45.557 


8 


12 


12.750 


12.090 


40.055 


37.982 


127.676 


114.800 


0.299 


1.254 


43.773 


8 


12 


12.750 


12.000 


40.055 


37.699 


127.676 


113.097 


0.299 


1.273 


49.562 


8 


13 


14.000 


13.250 


43.982 


41.626 


153.938 


137.886 


0.272 


1.044 


54.568 


8 


14 


15.000 


14.250 


47.124 


44.768 


176.715 


159.485 


0.254 


0.903 


58.573 


8 


15 


16.000 


15.250 


50.265 


47.909 


201.062 


182.654 


0.238 


0.788 


62.579 


8 



104 



HEATING AND VENTILATION 



the sheets from which it is made. For extremely high pressures, 
''extra strong" and ''double extra strong" pipe may be obtained. 
The extra thickness of the walls is added on the inside of the pipe, 
reducing the internal area and not affecting the outside diameter. 
These heavier grades are seldom used in heating work. 

91. Pipe Threads. — In order that they may be screwed to a 
tight joint, pipe threads are made with a taper of 1 in 32 with the 
axis of the pipe, and the threads in the fittings are tapped to the 
same taper. Pipe threads are commonly made to conform to 




90 Elbow 




Reducing 

Elbow 




Reducing 
Tee 




Cross 




Reducing 
Coupling 




45J:ibow 




Plug 



Cap 



Bushing 




Close Nipple 

Fig. 52.- 




Y Bend 




Shoulder Nipple 
-Screwed fittings. 




Coupling 



the so-called Briggs standard which calls for a thread having a 
60-degree angle, with the top and bottom slightly flattened. The 
number of threads per inch varies for the different sizes of pipe. 

92. Screwed Fittings. — The common forms of screwed fittings 
used in heating work are shown in Fig. 52. All except the 
ordinary couphng are made of cast iron. In designating reducing 
tees the size of the openings opposite each other is given first and 
then the size of the branch opening. For example, the reducing 
tee in Fig. 52 is a 1J4 by 1 by J^-inch tee. 

For pressures over 125 pounds, an "extra heavy" pattern is 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 105 

available which is suitable for working pressures up to 250 pounds. 
Extra heavy fittings are made with a greater wall thickness and 
are of larger dimensions throughout. 

93. Unions. — Where screwed fittings are used, provision should 
be made, at intervals in the line, for disconnecting the piping 
for repairs, etc. *' Right and left" couplings or ''unions" are 
used for this purpose. The former, as the name indicates, are 
couplings tapped at one end with a left-hand thread, so that both 




Lip Union 




Iron 

Iron, and Brass 
Union 

Fig. 53 



Iron Union with 
13rass Seat Ring 

-Pipe unions. 



threads can be screwed up simultaneously. Longitudinal ridges 
are cast on right and left couplings so that they can be identified 
after installation. 

For pipe sizes up to 2 inches, nut unions, consisting of two 
pieces screwed to the ends of the pipe and held together by 
means of a threaded nut are used. Flanged unions are used 
with larger sizes of pipe. In Fig. 53 are shown these various 
types of pipe connections. The ground-joint union is superior 






.Screwed Flange 



Welded Flange 



Improved Van Stone 
Flange 



Fig. 54. — Various forms of flanges. 



to the gasket union in that it can be disconnected repeatedly 
without trouble, whereas the gasket in the latter type must be 
frequently replaced. 

94. Flanged Fittings.- — Piping of the larger sizes is usually 
designed with flanged connections, in order that any section of 
pipe or any fitting can be readily removed. With screwed 
fittings it is necessary, in order to remove any member, to take 



106 



HEATING AND VENTILATION 



down all of the line from the nearest union or flanged connection. 
Flanges are commonly screwed to the pipe, especially for low- 
pressure work. For high-pressure work they may be welded to 
the pipe or attached by the ''Van Stone" method in which the 
pipe extends through the flange and is formed to a flat face as 
shown in Fig. 54. 

Some forms of standard weight flanged fittings are shown in 
Fig. 55. These fittings are suitable for pressures up to 125 
pounds. There is an extra heavy pattern of flanges and flanged 
fittings which differ both in general dimensions and in the number 
and spacing of the bolts. 






90 Elbow 



45 Elbow 



Eeducer 






Reducing Tee 



Tee 

Fig. 55. — Flanged fittings. 



95. Gaskets. — In bolting together flanged fittings it is neces- 
sary to insert a gasket between the faces in order to insure a 
tight joint. Gaskets are made of sheet rubber for water and 
low-pressure steam lines; for high-pressure lines gaskets of 
corrugated copper or of various compositions containing asbestos 
are used. Gaskets are preferably cut in a plain ring to fit inside 
of the flange bolts. 

96. Valves. — In Fig. 56 are shown the various types of valves. 
The gate valve is the form ordinarily used in steam piping. Globe 
valves are not permissible in horizontal steam lines as they are 
so constructed as to dam up the water and cause it to accumulate 
in the bottom of the pipe, but on vertical steam pipes and on 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 107 



water pipes they are permissible and are especially desirable 
when the flow of steam or water is to be throttled. The angle 
valve is a very good type of valve for locations where it can be 
used. 






Iron body gate 
valve non-ris- 
ing stem. 



Iron body globe valve 
rising stem. 



Angle valve. 




All brass gate valve. 



All brass globe valve. 
Fig. 56. 



Swing check valve. 



Valves in sizes up to 3 inches are made entirely of brass and 
the larger sizes are usually made of cast iron, with the gates and 
seats faced with bronze to give a non-corroding surface. The 
bronze mountings can be replaced when worn. The cover or 



108 



HEATING AND VENTILATION 



"bonnet" of these larger valves is bolted instead of screwed to 
the body. Gate valves are made either with a ''rising" or 
''non-rising" stem. With a rising stem valve the amount to 
which the valve is open is always apparent, which is often of 
great advantage but the space occupied by the valve is somewhat 
greater. 

Check valves are frequently used in heating work. The swing 
check illustrated in Fig. 56 is the most satisfactory form. 

97. Radiator Valves.^ — The ordinary radiator valve for steam 
is of the angle pattern and is provided with a union for connecting 
to the radiator, as shown in Fig. 57. The valve disc is made of 




Fig 



Ordinary radiator valve. 




Fig. 58.— Packless 



hard rubber and is renewable. These valves are also made in the 
"corner" pattern. 

The stem of the ordinary radiator valve is packed to prevent 
leakage with a soft stranded packing. The packing is seldom 
permanently tight, however, and the resulting leakage is often 
a source of considerable annoyance. In the more modern valves 
the packing is replaced by a grooved hard-rubber washer which 
is held against a seat by a spring. The construction of these 
so-called "packless" valves is shown in Fig. 58. Valves so. con- 
structed are much superior to the ordinary type, as all leakage 
and the necessity of renewing the packing are eliminated. 

The ordinary steam-radiator valve may be used in hot-water 
work. A special hot-water valve is made, however, which 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 109 



consists of a sleeve having an orifice equal to the pipe area. By 
a half turn of the hand-wheel the sleeve is turned so that the 
orifice is brought opposite the opening to the radiator. When 
closed, the valve allows enough circulation through the radiator 
to prevent freezing. Fig. 59 shows a valve of this type. 

98. Pipe Covering. — The piping of a heating system which is 
not intended to serve as radiating surface is insulated with some 
material of low heat conductivity. Most insulating materials 
owe their useful property to air enclosed in extremely small 
volumes. If the material is to be an efficient insulator these air 
volumes mus-t be so minute that the 
circulation of the air in them is re- 
duced to a minimum and in addition, 
the material itself must be of low con- 
ductivity. A satisfactory pipe cover- 
ing must also be able to withstand 
the effect of high temperature and 
vibration, and to retain its insulating 
qualities throughout a long period of 
years. 

The material which is probably the 
most widely used as an insulator is 
magnesium carbonate. It is in the 
form of a white powder, and some 
fibrous material such as asbestos fibers 
must be used with it as a binder, the 
aggregate being molded into blocks or 

into segments curved to fit the various sizes of pipe. Infusorial 
earth, which consists of the siliceous shells of minute organisms, 
is also combined with various binding materials to form a very 
efficient covering. 

Many forms of pipe covering are made of asbestos in combina- 
tion with some cellular material. The compound is rolled into 
sheets and the covering built up in corrugations so as to enclose 
air spaces. While not the most efficient type, these coverings 
are often the most suitable because of their low price. Fig. 60 
shoyvs a covering of this type. Hair felt, composed of matted 
cattle hair, is very efficient but cannot be placed in direct 
contact with steam pipes owing to its tendency to char at steam 
temperatures. 

In the selection of a pipe covering the cost of the pipe covering 




-Hot water radiator 
valve. 



110 



HEATING AND VENTILATION 



should be balanced against the saving which is effected by the 
reduction of the heat loss from the piping The most recent 
tests made on the commercial grades of pipe covering are those 




Fig. 60. — Cellular pipe covering. 



0.95 
0.90 



0.80 



No. VII Sall-Mo Expanded 
No.VI J-M Wool Felt 
No. IV J-M Eureka 
No.X Carey Duplex 
No-XIX Plastic 851 Magnesii 
No. XII Sall-Mo Wool Felt 



I 0.75 



S3 0.70 

CO 



^ 0.65 



S 0.60 



0.55 



H 0.45 

I 

0.40 



fl 



0.35 




50 100 150 200 250 300 350 400 450 500 
Temperature Difference, Degrees Fahrenheit 
(Pipe Temp. -Room Temp.) 
Fig. 61. — Results of tests by L. B. McMillan on single thickness pipe coverings. 

of L. B. McMillan and the results of his extensive investigations 
are shown by the curves in Fig. 61 which give the heat loss 



I 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 111 

through several commercial coverings of standard thickness for 
various temperature differences between the surface of the pipe 
and the air. 

It is seldom proper, in heating work, to install the most effi- 
cient covering, as the cost of such a covering may easily offset 
the decrease in heat loss obtained. In fact, the heat radiated 
from the covered mains and risers of a heating system is not 
entirely a loss as it is partially utilized. In general, where the 
steam temperature is high, the service continuous, and the coal 
expensive a more efficient covering is called for than in the case 
of low steam pressure and intermittent service, with a low-priced 
coal. 

99. Covering for Boilers and Fittings. — The exposed surfaces of 
heating boilers are usually covered with an insulating cement, 
composed of asbestos fibers and various fillers, which becomes 
plastic when wet. The cement is applied to the hot boiler with 
the hand to a depth of from 1 to 2 inches and bound with wire, 
after which a finishing coat of cement and a canvas jacket are 
applied. The pipe fittings are also covered with cement to the 
same thickness as that of the pipe covering. For large flanges 
and fittings removable coverings can be obtained which allow 
repeated access to the joints without damage to the covering. 

100. Air Valves. — In the ordinary steam heating system the 
air which fills the radiators when they are cold is forced out by 
the entering steam through some form of air valve installed on 
the end of the radiator opposite the supply connection. These 
air valves may be simply hand-operated cocks, which must be 
opened whenever the radiator is turned on, but the many forms 
of air valves which allow the air to escape but close automatically 
when steam reaches them, are greatly to be preferred. Automatic 
air valves are also designed to close when flooded with water as 
sometimes happens when a radiator does not drain properly 
or becomes filled with water because of a leaky inlet valve. 
The common design is illustrated in Fig. 62a. The composition 
post A expands when steam reaches it, causing the valve stem B 
to close against its seat. If water reaches the valve the inverted 
cup C, to which the valve stem B is attached, is raised by the 
buoyancy of the enclosed air and the valve closes. The force 
thus developed for closing the valve is small, however, and these 
valves cannot therefore be depended upon to prevent entirely 
the escape of water. The valve shown in Fig. 626 operates on the 



112 



HEATING AND VENTILATION 



same general principle, the expansion of a volatile fluid in the 
cylinder acting to close the valve when the steam reaches it 
and the cylinder serving as a float which closes the valve when 
water reaches it. While more expensive, this form of air valve 
is more reliable than the cheaper grades. It is always desirable 
to use air valves of good quality, as the faulty operation of an 
air valve is a source of extreme annoyance. 

Where large quantities of air are to be handled as in the case of 
a large riser or main, it is better to install a valve with a larger 
opening than that of the ordinary radiator air valve, so that the 
air can be discharged in a short time. Such air valves are com- 
monly called ''riser vents" and take the form shown in Fig. 62c. 





Fig. 62a. Fig. 62b. 

Air valves. 



Fig. 62c. — Riser vent. 



The valves used on an air-line system are intended to close 
against steam only. If water reaches them it is allowed to run 
into the air lines, from which it is drained at the lowest point. 
The expansion member may be either a composition post or a 
chamber containing a volatile liquid. The latter type is coming 
into general use. Fig. 63 illustrates these two types. 

101. Traps. — A steam trap is a device whose function is to 
drain the water from a steam pipe, separator, or radiator, with- 
out allowing steam to escape. For radiators, special traps of the 
float or thermostatic form described in Par. 82 are used. For 
draining steam lines and separators, there are two kinds of traps in 
use, designated as '' float " and " bucket " traps. The former ecu- 



1 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 113 

sists of a receiver having a discharge valve controlled by a float 
in such a way that a raising of the water level from an influx of 
water causes the float to open the valve, allowing water to be 
discharged by the pressure of the steam until the water level is 




Fig. 63. — Air line valves. 



lowered to its normal point. One design of float trap is shown in 
Fig. 64. A gage glass on the trap indicates the water level. 
There is normally several inches of water above the valve and the 
existence of the proper water level affords an indication that the 




Float trap. 



trap is operating properly. If the glass is empty, the trap is 
allowing steam to blow through; if it is full, the trap is not 
adequately taking care of the water. 

The bucket trap consists of a chamber containing a bucket 



114 



HEATING AND VENTILATION 



which is floated by the water in the chamber. To the bucket 
are attached the valve stem and valve, as shown in Fig. 65. The 
water flowing into the trap enters and fills the bucket, finally 
causing it to sink and thereby opening the discharge valve. 

The steam pressure forces the water out 
through the valve and empties the 
bucket, which rises and closes the valve. 
It is possible to lift the condensation 
by means of a trap to a height approach- 
ing that equivalent to the steam pres- 
sure, i.e., about 2.3 feet per pound pres- 
sure. It is better, however, if possible, 
to locate the trap so that it will dis- 
charge by gravity. 

There is another type of trap which is 
used where large quantities of water must be handled. This is the 
tilting trap, one form of which is shown in Fig. 66. The conden- 
sation flows by gravity into the chamber which is hinged on the 



Inlet 




Fig. 65. — Bucket trap. 




Fig. 66. — Tilting trap. 

trunnions A- A and balanced by the weight B. As the chamber 
fills, the weight B is overbalanced and the chamber falls, open- 
ing the discharge valve C. The pressure of the steam forces 
the water out through the discharge valve and when the cham- 



111 



PIPE, FITTINGS, VALVES, AND ACCESSORIES 115 



ber becomes empty, it tips back into the filling position and the 
discharge valve closes. The tilting trap in a slightly different 
form can be used for lifting the condensation from low-pressure 
piping to a considerable height, if high-pressure steam is avail- 
able. In such a trap an additional inlet valve is provided for 
the high-pressure steam, and the valves are so arranged that 
when the chamber fills and drops, the main inlet valve closes 
and the high-pressure inlet valve opens, admitting high-pressure 
steam which forces out the water and is capable of raising it to 
any height up to that equiva- 
lent to the steam pressure. 
Tilting traps are sometimes 
very useful but they require 
considerable attendance in 
order to insure their reliable 
operation. 

102. Separators. — The 
function of a steam separator 
is to remove condensation 
from steam lines. The sepa- 
rator accomplishes this by 
abruptly changing the direc- 
tion of flow of the steam and 
thereby causing the entrained 
water to be thrown out, by its momentum, against a suitably de- 
signed baffle, usually having a series of grooves which conduct 
the water into a receiver below. The water is discharged through 
a trap or seal. This form of separator is illustrated in Fig. 67. 
Separators are placed in the exhaust line from pumps and recipro- 
cating engines, where they remove the oil as well as the water 
from the steam. In choosing a separator care must be taken to 
select a size corresponding to the quantity of steam flowing rather 
than to the size of the pipe line, for a certain velocity through 
the separator is necessary to insure the elimination of the water. 

103. Reducing Valves. — Steam is occasionally supplied to a 
building at a pressure much higher than is necessary or desirable 
for heating purposes, making it necessary to employ a reducing 
valve, a simple form of which is illustrated in Fig. 68. The 
pressure on the reduced pressure side of the valve is transmitted 
through the balance pipe to the under side of the diaphragm, 
tending to close the valve. The force thus exerted is balanced by 




SIDE SECTION 
Fig. 67.- 



END SECTION 
-Steam separator. 



116 



HEATING AND VENTILATION 



that due to the weights w-w, and the valve will assume such 
a position that just enough steam will pass through it to maintain 
the required pressure on the reduced side, which pressure is 
governed by the position of the weights on the lever arm. The 
reduced pressure may be changed as desired by shifting these 




Reducing valve. 



weights. The valve shown in Fig. 68 is double-seated, so that 
its movement is independent of the steam pressure on either 
side of the discs and is controlled solely by the reduced pressure 
acting on the diaphragm. Reducing valves should be installed 
with a bypass so that they can be removed for repairs without 
interruption of the steam supply. 



., 



CHAPTER IX 
STEAM PIPING 

104. General Arrangement. — The elementary arrangement of 
the different systems of steam heating was shown diagrammat- 
ically in Chapter VII. Most of the principles involved in the 
design of the piping apply equally to all of them. 




Fig. 69. — One-pipe up-feed system. 

In Fig. 69 is shown the piping for a single-pipe upfeed system. 
The supply mains circle the basement, pitching away from the 
boiler, and are dripped at the ends into the return main. For 

117 



« 



118 



HEATING AND VENTILATION 



a two-pipe system, the return mains and risers would be arranged 
in a similar manner. 




Fig. 70. — Overhead vapor or vacuum system. 

Fig. 70 shows an overhead vapor or vacuum system in a tall 
building. Return risers extend from the top-floor radiators to 



STEAM PIPING 119 

the basement, where they tie into the main return Hne. In 
large buildings the first floor is often divided into small stores 
which require heat at times when none is needed in the remainder 
of the building and vice versa, making it desirable to install a 
separate main to supply the first-floor radiators and arranged so 
that it can be controlled independently of the main heating 
system. This scheme also has the advantage of making it 
much easier to install connections to the first-floor radiators 
which are often so located that it is difficult to reach them from 
the risers. In extremely tall buildings it is better to feed the 
risers from the bottom as well as from the top and a supply 
main is installed in the basement for that purpose. 

105. Principles Involved in Piping Design.^ — In designing and 
installing a system of piping, attention must be given to the 
following fundamental requirements: 

1. Provision for expansion. 

2. Proper drainage of condensation from the steam lines. 

3. Proper arrangement of piping and use of pipes of the proper 
size, so that the pressure drop due to friction will be small. 

106. Expansion.- — Perhaps the most important consideration is 
the proper provision for the linear expansion of the pipes. When 
steam is turned into or shut off from a system of piping, a change 
of temperature of the pipe of 140° to 170° takes place and pro- 
vision must be made for allowing the resulting change of length 
to occur without putting excessive strains on the fittings. The 
curve in Fig. 71 shows the theoretical expansion of wrought-iron 
pipe due to an increase in temperature from 60° to the 
temperature corresponding to various steam pressures. The 
temperature of 60° is assumed to be that at which the piping 
is originally installed. For low-pressure piping a rough rule is 
to allow 1 J-^ inches of expansion per 100 feet length of pipe. 

The force which an expanding pipe is capable of exerting is 
extremely great. If constrained at the ends with sufficient 
rigidity the increase in length will cause the line to ''bow" in 
the center, and the enormous strain thus imposed upon the 
flanges and fittings is almost certain to crack them. In designing 
any pipe line some point should be selected as a fixed or anchored 
point and a comprehensive study made of the amount and di- 
rection of the expansion. Provision must be made for prop- 
erly taking care of the elongation of all parts of the system. 

There are in general two ways in which the expansion in a 



120 



HEATING AND VENTILATION 



system of piping may be absorbed : (o) by the turning of some of 
the threaded joints and (h) by the bending of the pipes. The 
former method is necessary when the expansion is great but small 
movements can be readily absorbed by the spring of the pipes. 
Combinations of the two methods are also employed, as will be 
shown later. For very long and large pipes slip joints or special 
expansion fittings may be necessary but their use should be 
avoided wherever possible. 



















e 

i2.0 

u 

V 

Oi 

1 










-- 






y^ 


^ 












'1 1-0 

1 


/ 













































20 



140 



Fig. 71. 



40 30 80 100 120 

Steam Pressure - Lbs, per Sq, In. Gage 
Original Temperature 60 ° 
-Elongation of wrought iron pipe with various steam pressures. 



107. Drainage. — There is always some water in pipes carrying 
saturated steam. In some kinds of heating systems, in addition 
to the condensation formed in the pipe itself there is also con- 
densation from other pipes and from the radiators. The proper 
provision for the flow and drainage of the water is important. 
In horizontal pipes the water should if possible travel in the same 
direction as the steam and to accomplish this the pipes should be 
given a pitch of at least 1 inch in 10 feet in the direction of the 
flow. In case it is necessary to drain the condensation against 
the flow of the steam, as in a branch to a riser, a much greater 
pitch should be allowed and pipes of larger diameter should be 
used so that the velocity of the steam will be low. Any necessary 
pockets or low points where water might accumulate should be 
dripped. 



i 



STEAM PIPING 



121 



108. Mains and Branches. — Horizontal mains are usually 
anchored at the boiler and allowed to expand freely from that 
point. The amount of movement of any point along the length 
of the pipe is evidently proportional to its distance from the 
fixed point. In connecting risers and branches the movement 




Fig. 72a. Fig. 726. 

Methods of connecting branches. 

of the main is best taken care of by either of the arrangements 
in Figs. 72a and 726. As the main moves longitudinally the 
threaded joints c-c turn slightly. The arrangement of Fig. 726 is 
somewhat the better as the 45-degree elbow offers less resistance 
to the flow of steam than the 90-degree elbow in Fig. 72a. The 




P 



a 



Drip 



Fig. 73. 



Fig. 74. 



expansion of the horizontal branch is taken care of by the spring 
of the riser, which arrangement is quite permissible as such 
branches are rarely over 10 feet long. The arrangement shown 
in Fig. 73 is sometimes used when the expansion of the main is 
great. It has the disadvantage of offering considerable resist- 



122 



HEATING AND VENTILATION 



ance to the flow. Branches are sometimes taken from the 
bottom of the main as in Fig. 74. It is then necessary to in- 
stall a drip connection in the manner shown. This arrange- 
ment is undesirable in one respect. If for any reason the water 
level rises in the return system above the horizontal connection 
to the riser, then the riser will be entirely sealed from the main 
and its steam supply will be cut off. The one-pipe relief system 
is usually piped in this manner. 




Fig. 75. — Expansion swivel. 



Fig. 76. 



In very long horizontal mains in which the movement would 
be too great to be absorbed by the branch connections it is neces- 
sary to anchor the pipe at two or more points and to provide a 
swivel joint of the form shown in Fig. 75. One objection to this 
method is the resistance to the flow of steam offered by the 
fittings. 

Another scheme which is sometimes used where the main 
makes a turn of 90 degrees is that shown in Fig. 76. It will be 



OU 



Fig. 77a. Fig. 776. 

Advantage of eccentric reducer. 

noted that this does not give a perfect swivel joint but that the 
expansion must be partly absorbed by the spring of the members. 

When the size of the main is reduced an eccentric reducer 
should be used as in Fig. 77b so that no water pocket will_be 
formed. The accumulation of water in shallow pockets such as 
that formed by the reducing tee in Fig. 77a gives rise to severe 
cracking and pounding when the heating system is started up. 

109. Risers. — In small buildings where the supply mains are 
in the basement, the expansion of the risers is usually downward 



II 



STEAM PIPING 



123 



and the movement is taken care of by the spring of the branches 
and by the turning of the tees connecting the branches to the 
main (see Figs. 72a and 726). In larger buildings, where there 
is a main in the attic, the risers are anchored near the middle 

and the expansion takes place in 
both directions. When the expan- 
sion is too great to be handled by 
an ordinary branch connection the 





Fig. 78. — Flexible connection for 
riser. 



Fig, 79. — Expansion loop 
for riser. 



arrangement in Fig. 78 may be used. This gives a perfect swivel 
joint and is especially serviceable when the basement main must 
be installed near the foot of the risers. Its disadvantage is the 
resistance to the steam flow offered by the fittings. . 
The branch connection 

Q 



Last Brunch 
Connection - 



Air Valva 



Drip 



shown in Fig. 726 will easily 
take care of the expansion 
of risers about four stories 
high, and that in Fig. 78 
about eight stories. For 
taller buildings an expan- 
sion loop of the form shown 
in Fig. 79 is used. Such 
an expansion loop is easily 
capable of handhng a 
length of riser of at least 
four stories in either direc- 
tion and gives perfect flexibility, 
ring to conceal the loop. 

110. Drip Connections and Air Venting.— The ends of mains 
arfe dripped in the manner shown in Fig. 80. An air valve should 



Fig. 80. — Drip at end of main. 



Space is required in the fur- 



124 



HEATING AND VENTILATION 



be installed at such points to free the main of air when the system 
is started up. Drips from different mains should not be con- 
nected together above the water line as the pressure of the steam 
in them may be different, in which case the flow of the condensa- 
tion would be interfered with and a water-hammer set up. 

Air vents should be located at the ends of all mains and at 
other places where air is liable to become pocketed. 

111. Pipe Hangers. — The piping in a heating system must be 
substantially supported either from the building structure or 
from special supports. Horizontal mains are usually hung from 
the joists or steel work of the floor above. For pipes of moderate 
size the hanger shown in Fig. 81 is widely used. The perforated 





Fig. 81. — Simple form of pipe hanger. 

metal can be obtained in long strips and cut to any required 
length. This hanger is of low cost and can be installed very 
cheaply. 

For heavier pipes the hanger shown in Fig. 82 is a common 
design. The turnbuckle is used to adjust the elevation of the 
pipe when it is being installed. Both of these hangers permit 
the free longitudinal movement of the pipe line. Hangers 
should be placed at intervals of 20 feet or less on all horizontal 
pipes. 

Risers are supported at the anchor points in some such manner 
as is illustrated in Fig. 83. 



STEAM PIPING 



125 




Fig. 82. — Hanger for large pipes. 



4^ 

Elate ^ 



^ 



h' Plate 



past Tron 
4 ^ Block 



M' Dia. 






'TTTZZ^^^TTT^ 



ELEVATION 



PLAN 
Fig. 83. — Anchor for riser, i 



'From "Pipe-fitting Charts" by W. G. Snow. 



126 



HEATING AND VENTILATION 



112. Return Piping. — Return pipes of any kind of a steam 
system should be designed with ample provision for expansion 
as they may at times be heated to steam temperatures. Dry 
return mains should be given a pitch of at least 1 inch in 10 feet 
toward the boiler. Wet return mains should also be pitched 
toward the boiler so that they may be entirely drained of 
water when necessary. Return pipes should never be buried 
in the ground without protection. When it is necessary to con- 
ceal them the best plan is to arrange them in trenches with remov- 
able cover plates. An alternate scheme is to cover them with 
cylindrical tile with cemented joints which will keep out the water. 



if^Jr 




Fig. 84. — Water level in return line of vapor system. 



When buried in soil, return pipes corrode and deteriorate very 
rapidly. 

113. Vapor and Vacuum Systems. — In a vapor system, since 
the return lines are under atmospheric pressure, the water will 
build up in the return leg (Fig. 84) to a height above that in the 
boiler equivalent to the pressure in the boiler. In order to prevent 
the return mains from becoming flooded the distance from the 
water line of the boiler to the horizontal return main, designated 
by h in Fig. 84, should be as great as possible and should never 
be less than 2J'^ feet. In some cases it is necessary to place the 
boiler in a pit below the basement floor, in order to accomplish 



STEAM PIPING 



127 



this. The supply main of a vapor system can often be dripped 
at the end into the return main through a thermostatic trap. 
This, however, necessitates starting the return main at an eleva- 
tion below the end of the supply main which, with the necessary 
pitch toward the boiler, may bring it very close to the water 
line. A better arrangement is to install a separate drip line 
from the end of the supply main, which allows the return main 




Fig. 85. — Method of dripping supply main when basement is shallow. 

to be placed much higher. This arrangement is shown in Fig. 85, 
the dotted line representing the necessary elevation of the return 
main if the drip line is omitted. 

In an overhead vapor or vacuum system each riser is dripped 
at the bottom through a thermostatic trap as in Fig. 86. In 
order to catch the dirt and scale which would clog the trap a dirt 
pocket should be provided, consisting of a short capped pipe. 



Riser 



Dirt Pocket 




Trap 




Return Main 
Fig. 86. — Drip connection to riser, vapor or vacuum system 



Steam mains are dripped into the return line in a similar manner. 
Bypasses are sometimes provided for the most important traps 
to enable them to be easily cleaned or inspected and dirt strainers 
are also sometimes used. 

114. Valves. — The location of valves in a heating system 
should be given careful consideration. While valves are desirable 



128 



HEATING AND VENTILATION 



in many locations, there are also some places where they should 
never be used unless the plant is in the hands of a competent 
engineer, because of the possibility of accidents resulting from 
ignorant handling of them. 

In a small system as few valves should be installed as possible. 
Indeed for residence systems it is seldom necessary to install any 
valves except at the radiators. Valves should never be installed 
on the steam outlet of the boiler or on the return connection 
unless the plant is under careful supervision or unless two boilers 
are used in parallel, in which case valves are necessary in order 
to enable one boiler to be cut out of service for repairs. 

In large buildings a valve should be provided on each riser, 
if possible, so that the riser can be shut off for repairs, etc., 
without necessitating the shutting down of the entire system. 
Valves should also be provided on each branch main and return 
line in such buildings. Gate or angle valves should be used in 
preference to globe valves. 

115. Radiator Connections. — The connections to a radiator 
must be sufficiently flexible so that the main or riser is perfectly 



JI 



:# 




Fig. 87. — Connection to first 
floor radiator. 



Branch Exposed in Room Below 



Fig. 88. — Connections from risers where 
vertical movement is small. 



free to expand without straining the fittings. They must also 
be designed to allow the radiator to drain properly and must 
be free from water pockets. Figs. 87, 88, and 89 show some 
proper methods of connecting radiators in a single-pipe system. 
That shown in Fig. 87 is used for first-floor radiators connected 
directly to the main. The connection in Fig. 88 is suitable for 
risers whose. vertical movement is small enough to be absorbed 
by the spring of the horizontal pipe. An objection to this ar- 



STEAM PIPING 



129 



rangement is the fact that the connection is under the floor and 
inaccessible unless the horizontal branch is exposed in the room 
below as shown by the dotted lines. In the connection shown in 




Q) 



Riser— .w^P^ 



^ 



Fig. 



-Flexible connection, plan view — used when riser has considerable 
vertical movement. 



Fig. 89 a radiator valve of the ^'corner" pattern is used and the 
use of the elbows gives a very flexible combination which is well 



X 




suited for tall buildings where the movement of the risers is 
considerable. 



Fig. 91. — Wrong method. 

The connections to a radiator of a vapor system are shown in 
Fig. 90. These connections are also very flexible and the use 
of 45-degree elbows reduces the frictional resistance. 

In no case should a radiator be connected as in Fig. 91. The 
short, stiff connection allows no free vertical movement of the 
riser and causes severe strains on the fittings. 



130 



HEATING AND VENTILATION 



116. Pipe Coils. — Pipe coils may be connected in the manner 
shown in Figs. 92a and 926. The arrangement in Fig. 92a is 
used for a two-pipe system and that in Fig. 926 for a single-pipe 
system. A return connection is always used on pipe coils be- 
cause of the difficulty of draining the large amount of condensa- 




FiG. 92a. Fig. 92&. 

Methods of connecting pipe coils. 

tion formed in radiation of this type back through the inlet 
connection. The check valve in Fig. 926 prevents steam from 
entering the coil through the return connection. In order to 
open the check valve against the pressure of the steam in the 
riser a water head must be built up above it equivalent to the 
drop in pressure through the coil, which may be quite appreciable. 



Steam Main' 





\ /Check Valve 
.k!>?C^ ^^^<^eturn M 


lin 


Check 


I;/ \^ 


^ 




Valve 


/T^Blow-off Valve 


Connection 




93.- 


-Boiler connections 







II 



Therefore, a short length of vertical pipe should be installed 
above the check valve as shown, to receive the water column 
which would otherwise occupy the lower part of the pipe coil. 

117. Boiler Connections. — The usual method of arranging 
the connections to a steam boiler is shown in Fig. 93. In 



STEAM PIPING 131 

addition to the supply and return connections there is re- 
quired a blowoff cock and a city water connection with a shutoff 
valve and a check valve. It is sometimes necessary to connect 
two boilers in parallel. This must be carefully done so that there 
will be no chance of either boiler losing water to the other. 
Connections of ample size between both steam and return connec- 
tions should be made so that the pressure and water levels in 
both boilers will be always the same. 

118. Flow of Steam in Pipes. — When any fluid flows through 
a pipe a certain pressure is necessary to move it against the 
resistance caused by the friction of the fluid against the inner 
surface of the pipe. The following laws governing the friction 
of fluids in pipes have been estabhshed by experiment: 

1 . The total amount of f fictional resistance is independent of the 
absolute pressure of the fluid 

against the pipe wall. 

2. The frictional resistance 



varies nearly as the square of the Fig. 94. 

velocity. 

3. The frictional resistance varies directly as the area of contact 
between the fluid and the pipe wall. 

4. The frictional resistance varies directly as the density of the 
fluid. 

Consider a condition of steady flow in a pipe and let pi (Fig. 94) 
be the unit static pressure of the fluid, at one point and let p2 be 
the pressure at another point at a distance L from the first. The 
drop in pressure due to the friction of the fluid in passing through 
the distance L is then 

P = Pi - P2 

Expressing the laws of friction stated above in algebraic 
form we have 

Pa = FSDv^ (1) 

in which 

P = drop in unit pressure in pounds per square foot. 
a = cross-sectional area of the pipe in square feet. 
F = a. constant depending on the nature of the fluid and 

the nature of the pipe surface. 
S = area of contact between the fluid and the pipe in 

square feet. 
D = density of the fluid in pounds per cubic foot. 
v = velocity of the flow in feet per second. 



132 HEATING AND VENTILATION 

Then P = -FSDv' (2) 

f 
Let F be made arbitrarily = x" 

Then equation (2) becomes 

1 V2 

P = ^fSD^ (3) 

a 2g ^ ^ 

This is done simply to bring into the expression the term ^ 

which is the usual form for expressions of this nature. 

For round pipes of diameter d and length L, S = irdL and a — 

Let w = the weight of steam flowing in pounds per minute. 
Then w = '^XvXDXQO = Al.Udh^D 

P 

Let p be the pressure drop in pounds per square inch = v^ and 

let di be the diameter in inches = 12c?. 

Substituting in (4) these values for v, P and d we have 

p = 0.04839 •g^ (6) 

The coefficient / was found by Unwin to he = Kyi + jTrj) 

The value most commonly used for K for steam is that de- 
termined by Babcock which = 0.0027. 
Substituting in (6) we have 

p = 0.0001306 w^L (l + ^~) .^. 

Dd? 

in which 

p = pressure drop in pounds per square inch. 

w = weight of steam flowing in pounds per minute. 

L = length of pipe in feet. 

di = diameter of pipe in inches. 

D = average density of steam in pounds per cubic foot. 



STEAM PIPING 133 

The value of the coefficient / given above has been found to 
be correct for small pipes and comparatively low velocities. 
For large pipes and high velocities the value of / is considerably 
lower. ^ 

119. Factors Affecting the Size of Pipes. — The sizes of 
pipes to be used in a heating system depend upon several 
factors. The fundamental requirement as regards the supply 
pipes is that they must be of sufficient capacity to transmit the 
required quantities of steam with the pressure differential which 
is available. The latter depends somewhat upon the source of 
the steam supply. When exhaust steam from an engine or 
turbine is used for heating, it is best, from the standpoint of 
economy, to make possible the carrying of a low back-pressure 
by designing the heating system to operate with an initial pressure 
of not over 2 pounds per square inch. The same practice should 
usually be followed when steam is taken direct from a boiler, 
as it may be desired at some future time to use exhaust steam. 
The circulation will also be much better and the system more 
satisfactory if the pipe sizes are ample. When a vacuum pump 
is used the greater pressure differential thus set up makes possible 
the use of smaller pipes but it is well, nevertheless, to design the 
supply piping to operate as a gravity system with a moderate 
pressure drop so that the pump can be shut down at times if 
desired. The return pipes, however, can be made somewhat 
smaller if a vacuum pump is to be used. Another factor which 
makes an extreme reduction in the size of the supply pipes un- 
desirable is the noise caused by the resulting high velocity of the 
steam flowing through them. On the other hand, to make the 
pipes of excessive size increases unnecessarily the cost of the 
system. From a consideration of these various factors and of 
modern practice, a safe standard for the rate of pressure drop in 
the supply piping may be taken as from 0.03 to 0.10 pounds per 
100 feet of pipe. 

There are other factors beside that of pressure drop which affect 
the size of the supply pipes, such as the provision for the carrj^ing 
of condensation. In general all steam pipes in which the con- 
densation drains in the opposite direction to the flow of steam 
should be larger than if both flow in the same direction. This 

^See "The Transmission of Steam in a Central Heating System" by 
J. H. Walker, Trans. A. S. H. & V. E., 1917. 



134 HEATING AND VENTILATION 

applies particularly to single-pipe radiator connections and 
branches and to the risers of single-pipe systems. 

The proper size of return pipes is based upon experience and 
good practice as there is no definite law upon which their size 
can be computed. They must first of all be sufficiently large 
to carry the condensation. Second, they should be large enough 
so that they will not become plugged with dirt; and third, they 
must, in a vapor or vacuum system, be large enough to handle 
the air from the radiators as well as the condensation, when the 
radiators are first turned on. 

120. Selection of Sizes of Supply Pipes. — In a large or impor- 
tant system it is very desirable to make a detailed calculation of 
the pressure drop through the system. Besides insuring ample 
pipe sizes this will enable the pipe sizes to be reduced in some cases 
below those which would be chosen arbitrarily'-. In a large build- 
ing a considerable saving may be effected by judiciously choosing 
the pipe sizes for the risers and mains. In a vapor system the 
ideal condition would be to have approximately the same pressure 
at all radiator valves. To accomplish this fully would be of 
course an impossibility, but such a condition can be approxi- 
mated by careful design. In selecting the pipe sizes by the 
'^ exact" method, the desired pressure drop through the system 
is chosen and the approximate average drop per unit length of 
pipe is found, after which the exact drop can be computed by 
means of formula (7), Par. 118. In order to facilitate the cal- 
culations, the logarithmic chart in Fig. 95 has been prepared, 
from which the pressure drop per 10 feet of pipe can be read 
directly. The chart is based on an average density of the steam 
corresponding to a pressure of 2 pounds gage, which is sufficiently 
accurate for the range of pressure which occurs in a heating 
system. In figuring the capacities of the pipes no allowance 
need be made for condensation in the pipes themselves as this 
will ordinarily be negligible if the pipes are covered, but if the pipes 
are to be left bare their radiating surface should be included with 
that of the radiators. The scales at the bottom of the sheet 
read directly in square feet of radiation having an assumed 
heat transmission of 245 B.t.u. per square foot per hour, which 
is the amount which would be transmitted from 38-inch, two- 
column radiation with a room temperature of 70° and a steam 
temperature corresponding to the pressure of 2 pounds. The 
scales at the top of the sheet read in B.t.u. deUvered per hour, 



STEAM PIPING 



135 



and are convenient for use when the B.t.u. to be delivered by 
each radiator is known. As an example of the use of the chart, 
consider a riser 218 feet long supplying 3000 square feet of 
radiation. If the drop through the riser is to be not more than ' 
0.1 pound, find the proper pipe size. The drop of 0.1 pound 
in 218 feet is equivalent to a drop of 0.0046 pound in 10 feet. 
Passing vertically from the 3000-square feet point on the horizon- 

Use upper scale for pipe sizes 5"and over Heat Delivered per Hour Thousands of B.t.u.s. 

2,000 3,000 4,000 6,000.8,000 10,000 20,000 40,000 60.000 80,000100,000 200,000 

20 30 40 50 60 70 80 90100 200 300 400 500 600 800 1,000 2,000 

I I I I I I I I I I . I I I I I I I I I it I I I II. ] . t.' . .' . I I .1 I. .' I '. .1 '..I ' I. ' '.' I .'. '. ' .' ; ■ ■■.' 




50 60 70 80 90100 200 300 400 500 600 800 1,000 

5,000 10,000 20,000 30,000 40,000 60,000 80,000100,000 

■Use lower scale for pipe sizes 5"iand over Radiation Sq. Ft, 

Fig. 95. 



2,000 3,000 4,000 6,000 8,000 10,000 
200,000 300,000 



tal scale to intersect the diagonal lines for the 4-inch and 5-inch 
pipes we see that a 5-inch pipe will transmit the steam with a 
drop of 0.0026 pound in 10 feet and the 4-inch pipe with a drop 
of 0.0089 pound in 10 feet, which indicates that the 5-inch 
pipe is the proper size. 

The frictional resistance of the fittings must also be considered. 
It is'customary to reduce these resistances to equivalent lengths 



136 



HEATING AND VENTILATION 



of straight pipe, to be added to the actual length, according 
to the following table. 

Table XXVII. — Equivalent Resistance of Fittings 



Fitting 


Equivalent length of 

straight pipe expressed in 

no. of pipe diameters 


90-degree elbow 


40 


45-degree elbow 


20 


Tee 


40 


Reducing coupling 


40 


Valve 


60 







121. Example of Exact Method. — Consider the overhead vapor 
system shown diagrammatically in Fig. 96, and let it be required 
to choose the pipe sizes so that the pressure drop through the 
system will be between 0.3 and 0.5 pound. The equivalent 
length of each section of pipe should first be computed and set 



6420 A 



1 1 


y 

-B- 
o 


- 


-e- 


• 




1 

-Q 


■ 




■ 


Main Riser 








■ 


Boiler ^ 




- 




r 




Fig. 96. 

down in tabular form. Assuming a pressure of 2 pounds at the 
boiler, the pressure drop through each section of the main and the 
riser h-p, the longest path of the steam flow, is computed. The 
total length of the path being 387 feet, the average pressure 
drop may [be [taken as 0.4 -^ 38.7 = 0.010 pound per 10 feet 
ofipipe. The pressure drop through each of the successive sec- 
tions may then be computed from the chart in Fig. 95, using 



STEAM PIPING 



137 



the pipe sizes which will give as nearly as possible the average 
pressure drop determined above. The results may be arranged 
in tabular form as in Table XXVIII. 

Table XXVIII 



Section 


Equivalent 
length, ft. 


Rad. 
supplied 


Initial 
pressure 


Pipe 
size 


Pressure drop in section 


a-h 


130 


17,120 


2.000 


8 


0.0075X13.0=0.0974 


b-c 


20 


10,700 


1.903 


6 


0.0125X 2.0 = 0.0250 


c-d 


23 


9,090 


1.878 


6 


0.0090X 2.3=0.0210 


d-e 


19 


7,290 


1.857 


5 


0.0150X 1.9 = 0.0290 


e-f 


27 


5,510 


1.828 


5 


0.0090X 2.7=0.0240 


f-9 


23 


3,660 


1.804 


4 


0.0130X 2.3 = 0.0300 


g-h 


25 


1,960 


1.774 


3 


0.0170X 2.5 = 0.0420 


h-i 


15 


1,960 


1.732 


3 


0.0170X 1.5 = 0.0250 


i-j 


15 


1,700 


1.707 


3 


0.0130X 1.5 = 0.0190 


j-k 


15 


1,460 


1.688 


3 


0.0090X 1.5 = 0.0140 


k-l 


15 


1,220 


1.674 


23^ 


0.0220X 1.5 = 0.0330 


l-rri 


15 


980 


1.641 


2H 


0.0140X 1.5 = 0.0210 


m-n 


15 


740 


1.620 


2 


0.0220X 1.5 = 0.0330 


n-o 


15 


500 


1.587 


2 


O.OIOOX 1.5=0.0150 


o-p 


15 
387 


260 


1.572 


iy2 


O.OllOX 1.5 = 0.0160 



Final pressure at p = 1.556 pound 
Total drop = 0.444 pound. 

In systems of this kind it is desirable to have about the same 
pressure at all of the lowest radiators. The other risers, there- 
fore, can be designed for such a pressure drop that the pressure 
at the bottom of each will be approximately 1.556 pound. 

122. Approximate Method. — While the method outlined in the 
preceding paragraphs should be used for large or important 
installations, it is quite sufficient for many cases, to choose 
the pipe sizes simpty from the amount of radiation supplied. 
In Table XXIX are given sizes of mains and return lines for 
various amounts of radiation for all classes of systems. 

123. Radiator Connections. — In order to allow the condensa- 
tion to drain out against the inflowing steam the connections to 
radiators of one-pipe systems should be of ample size and the 
size of the nearly horizontal branches should be still more gener- 
ously proportioned. In two-pipe systems the radiator supply 
connections carry little condensation and may therefore be rela- 



138 



HEATING AND VENTILATION 



lively small. The sizes of connections commonly used for radia- 
tors of various capacities are given in Table XXX. 



Table XXIX.— Pipe Sizes for 


Supply and Return Lines 




Pipe size 


H 


V4. 


1 


m 


IH 


2 


2H 


3 


sy2 


Supply mains — all systems 






50 


100 

50 

300 
3,800 
1,500 


175 

100 

900 
6,000 
3,000 


350 

200 

2,000 

13,000 

6,000 


600 

300 

3,800 
23,000 
10,000 


1,000 

500 

6,000 
37,000 
18,000 


1,500 
700 


Upfeed risers! — one-pipe sys- 
tem 






Dry return lines — two-pipe 
and vapor systems 




50 


150 

2,000 

800 


10,000 
55,000 
30,000 


W^et return lines . 




Vacuum return lines 


100 


400 





Pipe size 


4 


5 


6 


8 


10 


12 


14 


16 


Supply mains — all systems 
downfeed risers, all systems . . 

Upfeed risers* — one-pipe sys- 
tem . .... 


2,000 

800 

13,000 
78,000 
40,000 


3,800 

1,300 

23,000 

65,000 


6,000 

1.800 

37,000 


13,000 

3,000 

78,000 


23,000 


35,000 


55,000 


78,000 


Dry return lines — two-pipe 

















* Which carry condensation from radiators. 



Table XXX. — Size of Radiator Connections 



One-pipe radiators 


Two-pipe radiators 


Size of 

radiator, 

square feet 


Radiator 
connection 


Horizontal 
branch 


Size of 

radiator, 

square feet 


Size of 

supply 

connection 


Size of 

return 

connection 


20 
24 
40 
60 
80 
100 
200 


1 
1 

IK 

iM 
IK 

2 


1 

m 
iM 

iM 

2 
2 


48 

96 

over 96 


1 

m 

13^ 


1 

IM 



Vapor and vacuum systems-supply % inch, return }4 inch. 
The size of pipe actually required to convey the necessary 
amount of steam is usually considerably less than these arbitrary 



sizes. 



STEAM PIPING 139 

124. Erection and Installation of Piping. — It is very necessary 
that the installation of a heating system be supervised carefully, 
as an immense amount of trouble can be caused by careless 
workmanship. 

One of the most important points is the proper threading and 
making up of the pipe joints. Sharp clean threads of the proper 
length should be the aim, the cutting of which requires that the 
threading dies be kept in perfect condition. In making up the 
joints the threads should be wiped perfectly clean and coated 
with a very small amount of pipe-joint compound. The use 
of too great a quantity of compound is a frequent and a serious 
mistake as the substance clogs the traps, valves, and return lines 
and is a continual source of trouble. 

Pipes of the 3-inch size and under are cut with a hand cutter 
which leaves a burr on the inside of the pipe. In the smaller 
pipes, especially, a considerable reduction in the internal diam- 
eter may thus be produced and the burr should therefore be 
removed with a reamer. 

The piping should be uniformly pitched and all air or water 
pockets should be avoided. Hangers should be installed in 
sufficient numbers and in proper locations so that no strains 
on fittings, valves, or boiler connections will be caused by the 
weight of the piping. 

One common source of trouble especially in new installations 
is the dirt which gets into the pipng while it is being installed. 
This dirt, consisting of cement, plaster, chips, etc. from the build- 
ing operations, and chips produced in threading the pipe, 
causes a great deal of damage in clogging the pipes, traps, and 
fittings and in cutting out the valve seats and discs. Most 
important of all, the open ends of the piping during installation 
should be kept carefully covered to prevent dirt from entering. 
Systems having traps on the radiators should always be operated 
for a week or two without the traps so that most of the dirt 
will be washed out before the traps are installed. 

125. Heating Systems in Connection with Power Plants. — 
In designing the piping for a heating system to be operated in 
conjunction with a power plant, provision must be made, first, to 
use the exhaust steam for heating, with a means for allowing the 
excess exhaust to escape automatically to atmosphere, and second, 
to supply live steam to the heating system during the hours when 
the heating requirements are in excess of the amount of exhaust 



140 



HEATING AND VENTILATION 



00 


c 


1 


^.^ 


1 t to 


B 

2 


— 1M_^ 



-4U 



UJa 




STEAM PIPING 141 

steam available. A common arrangement is that shown in Fig. 
97. The back-pressure valve, located on the main exhaust line, 
is so constructed that an increase of pressure over the amount for 
which the valve is set causes it to open and discharge steam to the 
atmosphere. The condensation from the radiators is discharged 
by the vacuum pump to the open feed-water heater from which 
it is taken by the boiler feed pump. A pressure-reducing valve 
with a bypass is used to feed steam direct from the boilers into 
the heating system when required. The reducing valve may be 
set to open when the pressure in the heating system, because of an 
insufficiency of the exhaust steam supply, drops below the re- 
quired point. The exhaust steam from the pumps is discharged 
into the main exhaust line, which, it will be noted, has a direct 
connection to the feed-water heater. 

Problems 

1. How much steam can be transmitted by a 64nch pipe 93 feet long 
with an initial pressure of 5 pounds gage and a final pressure of 4 pounds 
gage? 

2. How much steam can be transmitted by the same pipe as in Prob. 1, 
with an initial pressure of 105 pounds gage and a final pressure of 104 
pounds gage? 

3. What will be the drop in pressure if 2000 pounds of steam per hour 
are passed through a 5-inch pipe, 87 feet long, containing three 90-degree 
elbows? 

4. What initial pressure will be required if 110 pounds of steam per 
minute flows through a 4-inch pipe 70 feet long, the final pressure being 
51 pounds gage? Pipe has two 90 degree elbows. 



CHAPTER X 
HOT-WATER SYSTEMS 

126. Classification of Systems. — In a hot-water heating system 
the water flows in a closed circuit, absorbing heat while passing 
through the heater and giving up heat while in the radiators. 
The force required for moving the water through the circuit may 
be obtained from either of two sources. In the gravity or ''nat- 
ural" system, the force producing circulation is due to the dif- 
ference in weight of the hot water in the supply pipes and the 
cooler water in the return pipes; in the second class of systems 
the circulation is produced by means of a pump. 

Gravity systems are installed in residences and other build- 
ings of moderate size. Since the force producing circulation in a 
gravity system is small, the velocities are necessarily low and if 
a large quantity of water must be circulated, 
it becomes necessary to use very large pipes. 
Consequently, in large buildings or in 
groups of buildings where the heating re- 
quirements call for a large volume of water, 
it is best to employ a pump to produce a 
more rapid circulation, thereby permitting 
relatively smaller pipes to be used. 

127. Gravity System. — Theory of Flow. 
— As has been previously explained, the 
force which causes the flow in a gravity or 
Fig. 98. ''natural" system is due to the difference 

in weight of the water in the flow and re- 
turn pipes. Fig. 98 represents an elementary gravity system, 
consisting of a boiler and one radiator with an expansion tank. 
Consider that the system is in normal operation and that the 
heat added to the water flowing through the boiler is exactly 
equal to the heat leaving the water in the radiators and piping. 
The water leaves the boiler at the. temperature ti and enters the 
radiator at the temperature ^2, some heat having been lost during 
its passage through the pipe BC. In the radiator the water 

142 



c 


r 

F 


1 
I 


Heater J 


A 

i 


G 



HOT-WATER SYSTEMS 143 

temperature is reduced to the temperature ts, and during its 
passage through the return pipe EG it is further reduced to the 
temperature t^, at which temperature it enters the boiler. Let 
U be the average temperature of the water in the pipe C — J lead- 
ing to the expansion tank. 

Let H be the amount of heat which is delivered per hour by the 
radiator. Then if Q is the quantity of water flowing in pounds 
per hour 

H = Q(t2 - U) (1) 

The heat lost in the flow piping is 

Hi = Qih -U) 
and in the return piping 

H2 = Q{U - U) 

The heat added to the water at the boiler is 

H' = Q{h - U) 
Then 

H' = H -hHi-i- H2 

The density of the water at the various points in the circuit 
corresponding respectively to temperatures ^1, ^2, ^3, ti, and t^ 
is Di, Z>2, D^, D^, and D^. If the temperature drop is uniform, 
the average temperature in each section may be taken as the 
mean of the temperatures at the ends. The average density of 

the water in BC is then = ^' ^ ^' and in EG = ^' ^ ^' » 

Now consider the forces acting on each side of the plane A-A 
passed through the pjipe GB. The pressure on the left side is 

evidently due to the column of water BC of density ^ 

plus the column CJ of density D5 which is 

The pressure on the right-hand side is evidently 

Adding these pressures algebraically, we obtain for the result- 
ant pressure tending to move A-A to the left 
'Ds -f Da , (Di + D, 



K^-^)-K^-) 



144 HEATING AND VENTILATION 

Let D. = ^-t^.ndD. = ^-^ 

Then the unit pressure p' available for producing circulation is 
p' = h{D^ - D,) (1) 

It is evident that this pressure is the same at any point in 
the circuit BCEGB. It is independent of the relative lateral 
positions of the radiator and the boiler and depends only on the 
height h and the densities Dr and Dp. 

It is customary . to express this pressure as a ''head," i.e., the 
height of a column of water of the same density as that in the 
system which will produce the given pressure at its base. Let 
D be the average density of the water and hi the head equivalent 

v' 

to the unit pressure p'] then p' = hiD and hi = j^- Sub- 
stituting in equation (1) we have 

h(DR - D,) 



hi 



D 



hi is then the head available for producing circulation. If D, Dr, 
and Dp are expressed in pounds per cubic foot and h in feet, then 
hi will be in feet of water column. To express the head in inches, 
which is a more convenient unit, the right-hand member is multi- 
plied by 12, and 

h' = '^''^%- -^-) (2) 

The density D in equation (2) represents the average density of 
the water in the system. A close approximation would be to 
make 



D = 



Dr-\-Dp 



2 

Substituting in (2) 

h' = 24/? ^^ ~ ^^ C3) 

h' is then the available circulating head in inches of water. 

128. Friction. — The general expression for the loss of pressure 
due to friction for fluids in round pipes according to equation 
(4), page 132, is 



HOT-WATER SYSTEMS 145 

in which 

P = loss of pressure due to friction, pounds per square foot. 
/ = a constant depending on the nature of the fluid and 

of the pipe wall. 
D = average density of the fluid, pounds per cubic foot. 
V = velocity, feet per second. 
d = pipe diameter, feet. 
g = acceleration of gravity = 32.2. 
L = length of pipe in feet. 

To express the frictional resistance in terms of fluid head, 
let P = h" D in which P is in pounds per square foot and D 
in pounds per cubic foot, h" being the equivalent head in feet 
of the fluid at density D. 

Substituting in (4) 

^" = ^^ S (^) 

Let p = 4/, then ^" "= p\y ^^^ 

Now if V is expressed in inches per second, and d in inches, 
the head h" will be expressed in inches of water, without any 
change in the form of the expression, the inch unit being the 
more convenient. 

Equation (6) gives the frictional resistance to flow through 
straight lengths of pipe only. The resistance due to elbows and 
other fittings must also be taken into account. The resistance of 
such obstructions has been found to be nearly proportional to the 
square of the velocity of flow, and may therefore be expressed in 
the form 

in which a is a constant to be determined. The summation of all 
such '^ single resistances" may then be expressed as 

and the entire frictional resistance will be 

In order to impart to the mass of water in the system the 

10 



146 HEATING AND VENTILATION 

velocity v, a certain head must be used up in overcoming this 

''starting resistance" which is equal to ,^? in which g', 

the acceleration of gravity, is expressed in inches per second per 
second so that this last term will be expressed in inches of water 
head as are the others. The complete expression for the head 
required to start and to maintain flow may then be written 

In which h'' is in inches of water head. 

d is in inches. 

L is in feet. 

V is in inches per second. 

g is in feet per second per second. 

g' is in inches per second per second. 

In considering only the force required to maintain a steady 
flow, the last term does not enter, however. 

129. Condition of Steady Flow. — When the circulation in a 
heating system has become constant, the head available for 
producing flow must be exactly equal to the frictional resistance. 
This condition must invariably be fulfilled. If the available head 
increases or decreases, the velocity will change also until it 
assumes such a value that the frictional resistance will equal the 
available head. The relation ^ may be expressed by equating the 
right-hand members of equations (3) and (8) 

24/i y. — —~fr- = p~T ?r ^ 2a — (10) 

Dr + Df d 2g 2g 

130. Types of Gravity Systems. — Two-pipe Multiple -circuit 
System. — There are several different ways of arranging the 
piping in a gravity system. The most common method for 
installations of moderate size is the two-pipe multiple-circuit 
system shown in Fig. 99. The water leaves the boiler through 
the flow main, passes through the radiators and into the 
return main. A single pair of mains may be installed to circle 
the basement, but a better method is to install two or more 
pairs which extend in different directions. In order to insure a 

1 For further discussion see "Heating and Ventilation" by A. H. Barker, 

to whom the foregoing analysis is due. 



HOT-WATER SYSTEMS 



147 



sufficient flow of water to each radiator, it is best to provide sepa- 
rate supply and return risers to each radiator from the mains. 
Both the supply and return mains are given a pitch toward the 
boiler of about M inch in 10 feet, so that no air will accumulate in 
the piping and so that the system can be drained at the boiler. 
Two-pipe systems are often installed with a ''reversed" return 
main, as shown in Fig. 100. The flow in the return main is in 
the same direction as in the supply main and is so arranged that 
the length of the circuit through each radiator is the same. This 
tends to equalize the resistance to flow through all the radiators 
and the system therefore operates more uniformly throughout. 



□ 



J^ 



iQi 



□ 



^ 



G^ 



tgiR 



fO £1 






Fig. 99. — Two pipe multiple 
circuit system. 




Fig. 100. — Reversed return. 



A modification of the two-pipe system was formerly used, in 
which separate supply and return pipes were provided for each 
radiator. Although such an arrangement gives good results, 
the complication and cost of the piping have rendered it prac- 
tically obsolete. 

131. Expansion Tank. — The change of volume of the water 
in a hot-water system under varying temperatures is quite 
appreciable and an expansion tank must always be provided. 

The tank is located well above the highest radiator in the 
system and is provided with a ve"nt and an overflow to the sewer, 
as illustrated in Fig. 101. If located in an unheated room, a 
connection should be made to it from both supply and return 
mains to insure sufficient circulation to prevent freezing. If 
possible, the connection to the tank should be taken from the 
supply main as near the boiler as possible so that the air which is 
liberated from any fresh water which is fed to the boiler will rise 



148 



HEATING AND VENTILATION 



to the expansion tank and escape rather than accumulate in the 
radiators. 

The required capacity of the expansion tank is evidently a 
function of the quantity of water in the system and may be de- 
termined by computing the volumetric expansion, for the maxi- 
mum temperature range, of the es- 

timated quantity of water in the 
system. A rough rule is to make the 
capacity of the expansion tank in 

gallons equal to the radiation in 

square feet divided by 40. 



I 




Overflow and Yent 



( 


1 


, 






k 


a 1 
.2 

5 


1 ° 

1 i 
p. 

1 ^ 


^ , 


) 1 




) 


t 


J 









MWSW 



Fig. 101. — Arrangement of expansion 
tank.i 



Fig. 102. — Two-pipe overhead 
system. 1 



132. Two-pipe Overhead System. — In Fig. 102 is shown 
the two-pipe overhead system. The supply main is located 
in the attic and parallel supply and return risers drop to 
the basement as shown. This system is best adapted to rather 
large buildings. 

1 From " Pipe-fitting Charts " by W. G. Snow. 



HOT-WATER SYSTEMS 



149 



133. One-pipe System. — It is perfectly feasible to use a single 
pipe for both flow and return. A one-pipe overhead system 

is arranged as shown in Fig. 103. 

The return line from each radiator 
is connected to the riser at a point 
below the supply connection. The 
circulation through any radiator 
may be accelerated by lowering the 
point at which its return connec- 
tion reenters the riser, as at B. 

One disadvantage of this system 
is the fact that the cool water 
from the radiators lowers the aver- 
age temperature of the water in 
the riser and the radiators on the 
lower floors are therefore supplied 
with water at a relatively low tem- 
perature, so that they must have 
a larger surface. The advantages 
of the one-pipe system are its sim- 
phcity and somewhat lower cost. 

The one-pipe circuit systeni is 
shown in Fig. 104. The main 
circles the basement and separate 
connections are usually taken off 
to each radiator, although a first- 
floor and a second-floor radiator 
are sometimes connected to the 
same risers. The main should be 
of uniform size throughout its 

length. In large buildings, a separate main is sometimes in- 
stalled for each floor. This system has the inherent disadvan- 
tage of all one-pipe hot-water systems, that the temperature of 




Fig. 103. — One-pipe overhead 
system. 



i 




m 



Fig. 104. — One-pipe circuit system. 



the water in the main is lowered as that from the radiators is 
mixed with it and the radiators at the remote end must there- 



150 



HEATING AND VENTILATION 



fore be of larger size. Its chief advantage lies in its simplicity 
and in the smaller amount of piping required. 

134. Water Temperatures. — The water temperatures m a 
hot-water system will vary according to the heating re- 
quirements. Most ordinary gravity systems are designed to 
operate at a water temperature, leaving the heater, of 180° to 
190° and with a drop in temperature through the system of 20° 
to 30°. 

135. Study of Various Types of Systems. — Fig. 105 repre- 
sents a multiple-circuit system and Fig. 106 an overhead 
system. The head available for producing circulation through 
any radiator is proportional to the elevation of the radiator above 
the boiler, and to the temperature difference between the flow 
and the return as expressed in formula (3), page 144. In the 
two types of systems illustrated, the inlet and outlet connections 
of the radiators are both at the bottom and the effective height 
should therefore be measured from the radiator connections to the 



m 



u 



r^ 



43^ -H^T 




Fig. 105. 



Fig. 106. 



Fig. 107. 



center of the boiler. ^ The frictional resistance to flow varies 
directly as the length I of the circuit from the boiler through 
the radiator and the circulating head varies directly as the 
height h of the radiator above the boiler. It is therefore 
evident that the radiators marked D in both figures are the 

least favorably situated, since the ratio (yj is the least for these 

radiators. The size of the pipes in the mains must therefore 
be based on the circulating head due to these radiators. This 
can be more clearly comprehended when it is remembered that 
the source of the circulating force is the radiator itself. Radia- 
tors C and D, Fig. 105, may be thought of as centrifugal pumps of 
different working heads operating in parallel and pumping the 
water around the circuit. It is evident that in such a case if both 



HOT-WATER SYSTEMS 151 

pumps are to deliver water, the force producing circulation could 
not be greater than that developed by the pump having the 
smaller head, which corresponds to radiator D. 

If the pipes are well insulated, the effect of the small amount 
of heat lost from them will be negligible; if, however, they are 
left uncovered, the effect on the circulating head will be con- 
siderable. In the basement main system, a loss of heat in the 
flow mains and risers tends to decrease the circulating head, and 
a loss of heat from the return mains and risers tends to increase 
it. In the overhead system, a loss of heat from the flow mains 
and risers as well as from the return piping tends to aid circula- 
tion, while a loss from the main riser tends to retard it. This 
should be evident from a consideration of the direction of flow 
in these pipes. 

136. Single-pipe System. — In the single-pipe system, as illus- 
trated in Fig. 107, the water reaching the inlet connection of a 
radiator as at a, divides, part of the water passing through the 
radiator and part through the riser from a to h. The available 
head for producing flow through the radiator depends upon the 
distance a-h and the difference between the average temperature 
of the water in the radiator and the water in the pipe a-b. A 
lowering of the point at which the return connection from the 
radiator enters the riser, as at 6', Fig. 107, will tend to cause a 
greater portion of the water to flow through the radiator. 

The circulation through the mains and risers depends upon the 
lowering of the temperature in the risers themselves. The aver- 
age temperature in the risers is not necessarily the mean of the 
temperature at the top and bottom, but depends upon the pro- 
portion of the heat removed at the various radiators. 

137. Method of Computing Pipe Sizes. — In order to make 
certain that the system will operate with the same temperature 
drop and water quantities for which it is designed, it is necessary 
that the available circulating head be computed from the assumed 
temperatures and that the pipe sizes be so chosen that the fric- 
tional resistance will approximately balance this circulating head. 
This condition is expressed by equation (10), page 146, 

Dr -\- Dp d 2g 2g 

This calculation is, of course, made for the maximum condition. 
At other times the temperature of the water leaving the boiler. 



152 



HEATING AND VENTILATION 



and consequently the available circulating head, will be less 
than under maximum conditions. 

In Fig. 108 are given the values of the expression 24 jJ^ jf 

for various flow and return temperatures. To compute the avail- 
able circulating head, it is then only necessary to multiply the 
values obtained from the curves by h, the height of the radiator 



.50 

..48 
.46 
































































/ 
































Y 


.42 






























/ 


/ 




























/ 


/ 


/ 


.40 


























/ 


/ 


/ 


/ 


.38 
























/ 




/ 


/ 


/ 


.36 






















/ 


/ 


/ 


/ 


/ 




.34 






















// 


/ 


/ 


/ 


/ 




















4/0 


/ 


/ 




V 


/ 




.30 
















<e 


"M 


\/ 


/ 


/ 


/ 


' 


/ 


,^ ,r 














// /1 


y° 


/ 


/ 


/ 


/ 


Q .26 

+ .24 












.ff 


4^ 


// 


7 


,=. 


y 


/ 


, 


y 














/ 


Y 


/ 


/ 


% 


/ 


/ 


/ 


/ 


Q .22 
.20, 
.18 
.16 
.14 
.12 
.10 










S 




/ 


/ 


/ 


/ 


/ 


f 


/ 


/ 


/I 








/ 


/ 


/ 


/ 


/ 


/ 


/ 


/ 


^.^/ 




/ 


J 






/ 


/ 


/ 


/ 


/ 


/ 


/ 




/ 


/ 



^<^ 


/ 




/ 




/ 


^ 


/ 


/ 




/ 


/ 




/' 


y 


/ 


7 




/ 




/ 


/ 


/ 


/ 




/ 


/ 




/ 


/ 


/ 


/ 


-f/ 




/ 


y 


y 


/ 




/ 


/ 




/ 




/ 


/ 


/ 


/ 


* 


/ 


7 


/ 


/ 


' 


/ 


/ 


/ 


/ 




/ 


/ 


/ 


/ 


/ 


y 


\ 




/ 




/ 


/ 


/ 


/ 




/ 


/ 


/ 


/ 


/ 


/ 


"^/ 






/ 


/ 


/ 


r 


/ 




/ 




/ 


/ 


/ 


/ 


/ 


/ 


^ 




.04 


/ 


/ 




/ 




/ 




/ 


/ 


/ 


/ 


J 


V 








/ 




/ 




/ 




/ 




/ 




/ 




/ 









140° 150^ 160^ 170° 180^ 190° 200^ 
.Temperature -of Flow 

Fig. 108. 



210^ 220 



above the boiler. The height h should be taken from a point 
midway between the flow and return connections of the boiler. 
If both of the radiator connections are at the bottom, the distance 
Ifi is measured to the connections. If the inlet connection is at 
the top, the height In is usually measured to a point located at 
a distance above the bottom connection equal to one-fourth the 
height of the radiator. 



HOT-WATER SYSTEMS 



153 



In order to determine the pipe friction, it is necessary to 
know the value of p. This has been determined experimentally 
by many investigators, but their results differ considerably. 

0.0595 ^ 
According to Weisbach, p = 0.01439 + - — 7=^ for water m iron 

■\/v 

pipes, V being the velocity in inches per second. In order to sim- 











— 4r 


1 r^eysri 


^ 


!"f 


=^=-^ 


^=-f 


/---■ 










> 


s^s^ 


v.^ *^^ 


s P~ 


Z "/ Z2 


/^ t 


1 


40 








^''-U- 


mi^ 


^--N^ 


•^^^'^V- 


-"^ 7- 


J- /: 


1' 

-J 










^Hf 




^^=rA^ 


p^;;?- 


^^r--'-^ 


7^ >^ : 


-7- 














r^ 


f^t 


r- f 


7_ 7 


Z "y 










'^v^ 




■>>/ 


5^^"^' 


-t~ ^w 


'^ 7 ' -/ 












'■'-is 




/ s. 


/ ^'^^^ 


7 v>:t 


^/—^ 


i' 


a, 
S 10 






'p-.. 


i- 


1. L 


'-U 


;i=.c 


/ "7C 


^::^ 


t 
/ 


i? 


— 


%i: 




4=^ 


L. 


- P^ 

/ / 


'-,/--, 


'-y=T7 


^~7 /^ 




rr, *» 




^?>X 




^7 


^^ 


/ / 


y^^- 


i > 


^7""^^ - 




S 4 








f^K 


■V ^ 


i^-U 


z! z'^- 


-> --? 


^-v^ 




^ -, 


— 


h-v 


^-— .fT^H- 


Z" 3Z 


-1^ 


;^ T" 


y -^£ 


?"^"="- 




^, ^ 






^^c -T A» 


/ ■>-, 


/ 


y 


^-,2 y 


/ Z^- 


11 .^ 




a „ 






::^ 


/ 




f ^/ 


>^? 


/ / 


^z __ . 




a 2 






/ 


"^^ 


.V ]/ 


/ 


y 7^ 


--^-A 


/ 









-W-^ — 


/ 


A- 


7^ 




/ 1 


f::4 


/ 




it 






^^ 


/ 


r 
I 


r-f. 


Tf— ' 


—l-f- 






> .0 






y^y 


/ 


1 I 


/ 


3^T^ 


V '^ 






.4 






?--T^ 


. / 


y _ 




t %' 


^7-? 






03 

9> •> 


±^ 


S f, / 


?~ 


V^?' 




-^ —f 




^^J — 






.a -3 


^^ f 


/ 


/ / 


"^z " 


' / 


J 1 


/ "<^ 






.^ 


-^.7 


T -l 


/ 


r< 


/ 


t / 


7" 










7-- 


/ 


/ 


/ 


-.: 


/ L 


/Loss of 


Head by Fr 

for 
r in Iron Pi] 
ip. 160 Deg.] 

on the Fom 

^ d 29 
a which 

1439 + -^95 

sTxT 
jn by Weisb 

1 1 1 1 1 1 


iction 


1... 




7" 

—1—4 


-4^ 


/ 


/ 




^^/ / 


Wate 


pes 


»■»» 




ZZ 2 


-=r=^ 


^>^- 


-t — t 


- -h 


-Z-, - 


Ten 


F. 






y y*^ 


^::: 




t: 1 


/ 






. 






?^ / 




/ / 


1^ 




7- 7- - 






^=•.04 


-/ 


z:: 


^^''l^ 


/ f 


/-- 


-( ? 


^^^ — 


A = 






/- 


t -Zt 


-?-::3 


t 


-f 


^"y^ 


-f 










J / 


/ 71 


/ 


T I 


/ 


^ 


i 








7- A-^ 


/ / 


/ y 


1 


/ 


Z^ ::: 








/ 


/7 


"7^ 


'^ t 


J_ 


/ / 




P - X 




.01 


/ 


// 


/ / 


/ 


J I 


' / 




as giv< 

1 1 1 1 


ach 

1 1 1 1 


^ 


1 


i i 1 


11 i 1 


n" 


■0' ■** «r 


11 

00' 0* 


s s s 


iiill 
ssss § 


1 S 11 


IP. 
Ill 



Quantity of Water Flowing. -Pounds per Hour 
Fig. 109. 



plify the determination of frictional resistance under various con- 
ditions of flow, the chart in Fig. 109 has been constructed, based 
on Weisbach 's value for p.^ Having given the weight of water 

1 The results of later researches, not fully confirmed, indicate that the 
Weisbach coefficient is somewhat high and also somewhat in error in that it 
does not take into account any variation of the friction with the pipe diam- 
eter. However, the results obtained from its use are sure to be on the safe 



154 HEATING AND VENTILATION 

flowing and the pipe size, the resistance in inches of water can 
readily be taken from the chart. 

For the computation of the resistance of the fittings or ''single 
resistances," it is very convenient to consider that the resistance 
so introduced is equal to that of a certain length of pipe of the 
same diameter. Approximate determinations of the value of a 
indicate that at the average velocities occurring in heating work, 
the length of pipe in feet equivalent to a 90-degree elbow is 
equal to twice the number of inches diameter of the pipe. For 
example, a 3-inch elbow is equivalent in resistance to 6 feet of 
3-inch pipe. Values for the various single resistance are given 
in Table XXXI. 

Table XXXI. — Values of Single Resistances 





Equivalent length in feet 
equals diameter in 
inches multiplied by 


90-degree elbow 


2 


90-degree elbow — long sweep 

45-degree elbow 


1 
1 


Radiator 


4* 


Boiler 


4* 


Valve . 


lto2 







* Diameter of pipe connections. 

The procedure in calculating the pipe sizes according to the 
accurate method is then as follows: The piping is completely 
laid out according to the system chosen, i.e., whether overhead 
or with basement mains, etc. The circuit supplying the most 
unfavorably situated radiator is the first to be considered. The 
pipes in this circuit are assigned tentative sizes and the single 
resistances noted and the equivalent lengths obtained from Table 
XXXI. The total equivalent length of each section of the cir- 
cuit is then computed and the friction drop taken from the curves 
in Fig. 109. The available circulating head must next be com- 

sidc and it has been used in the design of many successful installations. For 
further discussion see : 

"The Determination of Pipe Sizes for Hot Water Heating Systems," by 
F. E. Geisecke, Trans. A. S. H. & V. E., 1915. 

"The Friction of Water in Iron Pipes and Elbows," by F. E. Geisecke, 
Trans. A. S. H. & V. E., 1917. "The Mechanics of Heating and Ventilat- 
ing," by Konrad Meier. "Heating and Ventilating'.' by A. H. Barker. 



HOT-WATER SYSTEMS 155 

puted. From the curves in Fig. 108, the value of 24 j J^ . jf 

is found for the flow and return temperatures which have been 
assumed. This value, multipHed by the height in feet of the 
radiator under consideration, above the boiler, gives the circulat- 
ing head in inches of water. If the friction head does not agree 
within about 5 per cent, with the circulating head, as it probably 
will not in the first calculation, the size of some of the pipes in 
the circuit must be changed and the total friction drop again 
computed. By successive refinements the two quantities can be 
made nearly equal. This circuit having been established, the 
circuits to the other radiators are worked out in a similar manner, 
the parts in common with the circuit first computed being left 
as first set down. In the case of a single-pipe system, the cir- 
culation to the most unfavorably situated riser is first computed, 
with the circulating head taken as that due to the riser. 

138. Necessity of Accurately Choosing the Pipe Sizes. — ^Let 
us examine the effect of an improper selection of pipe sizes. 
There are three possible ways in which errors can be made. 

I. By making all the parts of the system too small but of the 
proper relative size. 

II. By making all of the pipes too large. 

III. By making the resistance of some circuits much greater 
than that in the others. 

If the pipe sizes are all too small, the primary effect will be to 
decrease the quantity of water passed through the entire system 
in unit time. If the temperature of the water leaving the boiler 
is kept constant, the effect of the decrease in the quantity will be 
to increase the temperature drop in the radiators. This will 
increase the available circulating head which will in turn increase 
the velocity of flow. Unless the error is extreme, the system will 
therefore approach the performance set for it. 

If the pipes are too large throughout, the primary effect will be 
to increase the flow of water through the system. This will cause 
a decrease in the temperature drop through the radiators, a reduc- 
tion in the circulating head, and a consequent reduction of the 
flow to some value approaching the proper one. The same action 
takes place in the case of the individual circuits or radiators. 
If the pipes are too small, the reduction in flow causes an increase 
in the temperature drop and the net result is usually but a slight 
decrease in the heat delivered to the room. 



156 



HEATING AND VENTILATION 



It is thus apparent that gravity hot-water systems are to some 
extent self -regulating. It is due to this property that the ordinary 
hot-water systems, installed without exact design, operate with 
satisfaction. Indeed, for the usual small system it is not practi- 
cable to make exact calculations of the pipe sizes, experience 
having evolved ''rules of thumb" which give pipe sizes which are 
on the safe side and produce entirely acceptable results. While 
the heat delivered to the rooms may vary by several per cent, from 
the theoretical requirements, the error is well within that due to 
inaccuracies in computing the heat losses from the room. 

In large installations, the exact method has some distinct 
advantages. The liberality with which the pipe sizes of a small 
system are selected cannot be practised on a large system without 
a considerable increase in the cost of the installation, while any 
pipes which may be chosen too small can be replaced only at great 
expense. Throttling valves, while they should be placed on the 
branch circuits as a precaution, are difficult to adjust and are 
easily tampered with. A calculation of the pipe sizes in the 
manner outlined is therefore desirable for large or important 
installations. 

139. Approximate Rules for Pipe Sizes. — Table XXXII gives 
the capacity of mains of various pipe sizes for different kinds of 
systems. 

Table XXXII.— Size of Mains 

Assumed Length 100 Feet, Temperature Drop in Radiators 20° 





Capacity, square feet of direct radiation 


Pipe diam. 


Two-pipe upfeed 


One-pipe upfeed 


Overhead 


IM 

13^ 

2 

2M 
3 

4 
5 
6 

7 

8 


75 

110 

200 

310 

540 

780 

1,100 

1,900 

3,000 

4,300 

5,900 


45 

65 

121 

190 

330 

470 

650 

1,100 

1,800 

2,700 

3,500 


130 
190 
340 

530 
920 
1,330 
1,800 
3,200 
5,000 
7,200 
9,900 



Table XXXIII gives the capacity of risers in square feet of 
radiation. 



HOT-WATER SYSTEMS 



157 



Table XXXIII. — Size of Risers 
Assumed Temperature Drop in Radiators, 20° 





Upfeed 


Downfeed risers, not 
exceeding four floors 


size 


First 
floor 


Second 
floor 


Third 
floor 


Fourth 
floor 


1 


33 


46 


57 


64 


48 


134 


71 


104 


124 


142 


112 


13^ 


100 


140 


175 


200 


160 


2 


187 


262 


325 


375 


300 


23^ 


292 


410 


492 


580 


471 


3 


500 


755 


875 


1,000 


810 



The following schedule of tappings is used for hot-water 
radiators : 

Table XXXIV. — Radiator Tappings 

Size of radiator Supply and return tappings 

Up to 40 square feet 1 inch 

40 to 72 square feet l}i inches 

Over 72 square feet 1}^ inches 

140. Piping. — Many of the principles governing the design 
of steam piping apply to hot-water work. Expansion must be 
provided for with care, although it is less in amount. Connec- 
tions and fittings must be installed so as to interpose as little 
resistance to flow as possible. The venting of the air from the 
system is important. In addition to a vent at the expansion 
tank, a small pet-cock should be provided at each radiator and 
at any other points at which air may accumulate. Mains should 
be given a pitch of at least }i inch in 10 feet toward the boiler 
and provision should be made for draining the water from the 
entire system as is necessary when the plant is shut down in cold 
weather. 

141. Closed Systems. — In the open-tank systems which have 
been described, the water temperature is limited to 212° because 
the pressure at the top of the system is at atmosphere ; but if the 
pressure of the water at the top of the system is raised above 
atmosphere, its boiling point and consequently the allowable 
temperature is raised, increasing the heat output of the system 
For maintaining the increased pressure on the system, some 
device such as a mercury seal is inserted in the pipe leading to the 
expansion tank. One form of these so-called '' generators'' is 



158 



HEATING AND VENTILATION 



shown in Fig. 110. The water from the system, as its tempera- 
ture rises, exerts an increasing pressure on the surface of the 
mercury in the chamber B, forcing mercury up the tube A until 
it bubbles out of the top of the tube. A pressure equivalent to 
the height of the mercury column thus formed may be built up 
at the top of the system and the water may be heated nearly to 
the corresponding boiling point. As the water in the system 
cools and decreases in volume, the mercury falls down the tube 
and more water enters the system from the expansion tank. 




Fig. 110. — Mercury seal "generator." 

Generators are especially useful for increasing the output of a 
heating system which has been inadequately designed or which 
has become inadequate. 

142. Forced Circulation. — When hot-water heating is used in 
large buildings or groups of buildings, the circulating power is ob- 
tained from a pump and smaller pipes are used, the water flowing 
at much higher velocities than in a gravity system. In systems 
employing forced circulation, the water usually passes through 
the pump, then to the heater, and to the radiators. The piping 
is arranged in the same general manner as in the gravity systems. 
The action is somewhat different from that in the gravity systems 



HOT WATER SYSTEMS 159 

in that the force producing circulation is from the pump and not 
from the cooHng action of the radiators; for although the tempera- 
ture difference in the system has some effect, it is so far over- 
balanced by the force exerted by the pump as to be negligible. 
The flow through the various parts of the system is therefore 
governed to a greater extent by the frictional resistance, as the 
system does not possess the self-regulating qualities of the 
gravity system. 

143. Pumpage, Friction, and Temperature Drop. — The quan- 
tity of heat delivered per hour may be expressed by the equation 

H = Q (h- U) (1) 

in which H = quantity of heat delivered per hour. 
Q = weight of water pumped per hour. 
h — t2 = drop in temperature of water. 

It is evident that the quantity of water and the temperature 
drop may vary, the requirement being that their product remain 
constant. As the temperature drop is increased, however, the 
average temperature of the radiators is lowered and somewhat 
more surface must be installed. It is common practice to allow 
a temperature drop under maximum conditions of about 20°. 

Before a circulating pump can be intelligently selected, it 
is necessary to choose the differential pressure at which the system 
is to be operated. If a large pressure drop is allowed, the pipes 
can be made relatively small, but the power required for pumping 
the water will be greater. Although it is true that the energy 
used up in friction is converted into heat and is therefore utilized, 
the energy thus recovered is only a portion of the energy input 
to the pumping unit. The cost of the power must therefore be 
taken into consideration. If the pump is steam-driven and the 
exhaust used for heating the water, the cost of power will be 
lower than if current is purchased for a motor-driven pump. In 
each case a study should be made, balancing the annual invest- 
ment charges of the piping system against the cost of power to 
determine the most economical combination. The pressure 
drop usually allowed is from 10 to 30 pounds. The velocity of 
flow in the pipes is limited to about 40 inches per second in build- 
ings where the noise produced by a higher velocity would be 
objectionable. In industrial buildings, no such limit is imposed. 

144. Calculation of Pipe Sizes. — The calculation of the 
pipe sizes in a forced circulation system is much more im- 



160 



HEATING AND VENTILATION 



portant than in a gravity system, because the former does not 
possess the ''self-regulating" property of the gravity system. If 
any one circuit is unfavorably designed, there will be a tendency 
for it to be short-circuited. Furthermore, the resistance of the 
entire system must be made approximately equal to the rated 
head of the pump. The procedure in designing a forced cir- 
culation system is as follows. The heat loss from the building 
having been computed, the temperature drop in the radiators is 
chosen and the amount of water to be supplied per hour is com- 




.FlG. 111. 

puted from formula (1), Par. 143. From a consideration of the 
various factors mentioned in the preceding paragraph, the dif- 
ferential head is chosen and a pump is selected which will operate 
most efficiently under the given conditions. The piping must 
then be designed so that this differential pressure is used up in 
friction. 

The general scheme followed in choosing the pipe sizes is 
similar to that used for a gravity system, the available circulating 
head, which in this case is produced by the pump, being balanced 
by the pipe friction. 



HOT-WATER SYSTEMS 



161 



The method can best be explained by working out a specific 
installation. In Fig. Ill is shown diagrammatically one part 
of an overhead two-pipe system. The weight of water flowing 
per hour is indicated for the circuit which supplies the radiator 
marked 30-41, the assumption being made that these water 
quantities have been computed in the manner previously ex- 
plained. The circuit through this radiator is the longest and 
should therefore be computed first and the other parallel circuits 
designed to give the same resistance. In column 2, Table 
XXXV, the actual length of each section of the circuit is given. 
The system will be designed on a basis of a pressure differential 
of 10 pounds. The length of the circuit is 481 feet. The average 



Table XXXV. — Calculation of Pipe Sizes — Forced Circulation 

System 



§ 

•43 
o 

a 


II 

0?54 a 


i 

o 


si 


i 

G 
03 

."2 

I 

a 


a 
> 


2^ 

u a 

|| 


« 

03 

3 


J s 


i 
1 


c 

> 

0^ 


2^ 

11 
1^ 


C 

1 

1 


1 


^ 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


1-2 
2-3 
3-4 
4-5 
5-6 

6-30 
30-41 
41-42 
42-43 
43-44 

44-45 
45-46 
46-47 
47-48 
48-49 

49-50 
50-51 
51-52 
52-53 
53-54 

54-29 
29-55 


106,470 

106,470 

91,260 

76,050 

60,840 

15,210 
1,667 
1,667 
3,000 
4,333 

5,667 
7,000 
8,333 
9,667 
11,000 

12,333 
13,667 
15,210 
|60,840 
76.150 

91,360 
106,470 
Total. . . 


4 
4 
3 
3 
3 

2 
1 
1 

1 
1 

IM 
Ui 

m 

IH 
VA 

2 
3 
3 

3 

4 


21 

158 

22 

22 

22 

10 
8 
12 
12 
12 

12 
12 
12 
12 
12 

12 
12 
3 
22 
22 

22 
29 


1X8 
3X8 

1 X 4 
2X2 

1 X 4 
3X8 


29 
182 
22 
22 
22 

14 

12 
12 
12 
12 

12 
12 
12 
12 
12 

12 
12 
7 
22 
22 

22 
53 


4.0 
4.0 
9.4 
6.8 
4.6 

2.4 
0.9 
0.9 
2.8 
5.2 

2.7 
3.9 
5.3 
3.3 
4.1 

4.9 
5.9 
2.4 
4.6 
6.8 

9.4 
4.0 


11.6 
72.8 
20.7 
15.0 
10.1 

3.4 
1.1 
1.1 
3.4 
6.2 

3.2 
4.7 
6.4 
4.0 
4.9 

5.9 

7.1 

1.7 

10.1 

15.0 

20.7 

20.2 

249.3 

8.8 




1 X 3 


22 
13 

22 


9.0 

7.5 

9.0 


19.8 
9.8 

19.8 
275.1 




Pounds 




















9.7 























11 



162 HEATING AND VENTILATION 

friction loss per 10 feet of pipe in inches of water column at a 

10 y 1728 
temperature of 160° will be 40 1 v^ n i~7j = ^-9 inches of v/ater. 

With the given quantities of water flowing, and using a friction 
loss of approximately 5.9 inches per 10 feet, the pipe sizes can 
be chosen from the chart in Fig. 109, page 153. They are set 
down in column 3. The length equivalent to the single resist- 
ances is computed and the total equivalent lengths set down in 
column 6. From the friction chart the resistance per 10 feet 
for each section is found. These are multiplied by the equiva- 
lent lengths and the results set down in column 8. The sum 
of all of them is found to be 249.3 inches of water which is equal 
to 8.8 pounds as against the 10 pounds originally specified. The 
sections 5-6, 6-30, and 52-53 may be decreased one pipe size 
to increase the resistance, as given in columns 9 to 13. The 
total resistance will then be 275.1 inches or 9.7 pounds which 
is sufficiently close to the desired resistance. The circuit 2-3-5- 
53-29-55 and all of the remaining circuits must then be worked 
out in a similar manner to give an equal resistance, the parts 
which have already been computed being left as they stand. 
It is desirable to install a ''lock and shield" valve on each riser 
and at each radiator in order that the distribution can be ad- 
justed after the system is completed. 

145. Pumps. — Either the centrifugal or the reciprocating pump 
may be used to produce the circulation ; but the centrifugal type 
is by far the more suitable. It possesses the advantages of pro- 
ducing a uniform flow of water, does not transmit jars or vibration 
to the piping, requires little attendance, and is economical in 
operation. Centrifugal pumps may be driven by either a steam 
turbine or a motor, the former drive being used when high-pres- 
sure steam is available. 



CHAPTER XI 
AUTOMATIC TEMPERATURE CONTROL 

146. Manual Control. — In every heating system the radiators, 
boiler, and other component parts are selected on the basis of the 
maximum requirements, i.e., for the lowest outside temperature 
which is to be expected. Consequently the capacity of the sys- 
tem is much greater than is required in average winter weather. 
In many localities, for example, where heating plants are de- 
signed for a minimum outside temperature of 0°, the average 
temperature for the heating season is from 35° to 40°. In 
order to prevent excessive room temperatures the heat output 
of the system must be regulated, either manually or automatically, 
to correspond approximately with the heat losses from the 
building. 

Temperature control is accomplished in different ways accord- 
ing to the kind of heating system and the nature of the building. 
In many cases manual control of the radiators or of the furnace 
drafts is all that is necessary; in other cases, automatic tem- 
perature control, applied to the individual radiators, is very de- 
sirable. In hot-air furnace installations and in small steam and 
hot-water systems the universal method is to regulate the heat 
output of the boiler or furnace by adjusting the drafts. When 
the building is large, however, it is often impossible to regulate 
accurately the temperature throughout the building by this 
means and control of the radiators must be resorted to. In 
vapor systems equipped with graduated inlet valves accurate 
control is possible if sufficient attention is given by the occupants 
of the room to the adjustment of the valves. In single-pipe 
steam systems the supply of steam to each radiator cannot be 
controlled and it is therefore sometimes desirable to provide at 
least two radiators in each room so that one or both can be used 
as required. 

In a vacuum steam system the heat output can be varied within 
certain limits by varying the steam pressure. For example, if the 
steam pressure could be varied from 10 inches of vacuum to 10 

163 



164 



HEATING AND VENTILATION 




Fig. 112.— Bellows 
thermostat. 



pounds pressure, the temperature of the radiating surfaces would 
be increased from 193.2° to 240.1°, which, if the room temperature 
is 70°, would give a range of heat output of about 38 per cent. 
This is about the maximum range which could be secured by this 
means. 

147. Automatic Control Applied to Boiler or Furnace. — Tem- 
perature control by adjusting the drafts of the boiler or furnace 
can be accomplished automatically by 
means of any one of several designs of 
thermostats. The simplest of these con- 
sists of a bellows containing a volatile 
liquid which causes an expansion and con- 
traction of the bellows with changes of 
temperature. The bellows is installed at 
the point from which the temperature is to 
be controlled and its movement is trans- 
mitted by means of a cable to the dampers on the boiler or fur- 
nace in such a way that a lowering of the room temperature 
causes an increase in the air supply to the fuel bed and a result- 
ing increase in the heat output. This form of thermostat is 
shown in Fig, 112. 

In another form of thermostat 
the dampers are operated by a 
motor located in the basement 
and started electrically from a 
controller placed in the room 
above. Fig. 113 illustrates the 
controller of such a thermostat. 
The member A consists of two 
strips of metals, having different 
coefficients of expansion, brazed 
together. This member is fixed 
at point B and the end C is 
deflected to the right or left by 
the unequal expansion of the 
metals with changes of tempera- 
ture. The controller is connected electrically with the motor 
in such a way that, as the temperature drops and the strip C 
makes a contact with D, a current of low voltage is transmitted 
through the circuit, and, by means of a relay, starts the motor, 
which opens the drafts on the boiler. Similarly, a slight increase 



^^r\ 




Fig. 113. 



-Controller for damper 
thermostat. 



AUTOMATIC TEMPERATURE CONTROL 



165 



of temperature above the established point causes a contact to 
be made between C and E and the motor is started, closing the 
drafts. The temperature for which the controller is set can be 
changed by moving the knob F which shifts the position of D 
and E. The controller can be obtained with a clock mechanism 
which will cause the drafts to close at night and to open in the 
early morning at some predetermined time. 

The motor may be a clock mechanism, in which the energy is 
obtained from a spring which is wound periodically by hand. 



Wire 




Fig. 114. — Method of connecting thermostat. 



The electric motor is more desirable, however, as it requires no 
winding. The method of connecting the motor to the dampers is 
shown in Fig. 114. 

In installing this form of thermostat the location of the con- 
troller is of prime importance. As the heat supply for the entire 
building is to be controlled from one point, it is essential that the 
controller be installed in some central location where the tem- 
perature is approximately an average of that in the entire 
building. It is the difficulty of controlling the temperature 
satisfactorily from a single point that limits the use of such 
thermostats to residences and small buildings. 



166 



HEATING AND VENTILATION 



Air Inlet 



148. Automatic Control Applied to Individual Radiators. — 

In large buildings, in order to regulate the temperature auto- 
matically, the radiators in the various rooms must be operated as 
separate units, by means of a controller located in each room. 
The power for operating the radiator valves is obtained from 
compressed air, supplied from a central source, and the air sup- 
ply to the individual radiator valves is regulated by a small valve 
operated by the expansion element in the controller. The system 
may be designed so that the radiator valves are either fully open 
or fully closed, or the amount of opening may be graduated 
according to the room temperature. The former arrangement is 
necessary on single-pipe radiators and is 
known as the '' positive" type, while the 
laXter or 'graduated" type is applicable 
to steam radiators having a separate re- 
turn connection and to hot-water radiators. 
The type of radiator valve used is shown 
in Fig. 115. The valve is closed when air 
under sufficient pressure is admitted above 
the diaphragm A . When the air pressure 
is released the springs BB force the valve 
open. If a pressure less than that re- 
^ , _ ^ ,. quired to close the valve exists above the 

Fig. 115. — Radiator ,. , i i -n i 

valve for compressed air diaphragm the valve Will take an inter- 
system of temperature mediate Dosition depending on the amount 

regulation. x i i 

of that pressure. In the graduated system 
the intermediate positions of the radiator valve are obtained by 
creating this partial pressure. 

A common design of compressed-air thermostat of the gradu- 
ated type is shown in Fig. 116. The thermostatic element is 
the hard-rubber cylinder A. The valve G is closed while the 
room temperature is up to normal and the full air pressure is 
transmitted through the inlet C, the restricting valve S, and 
the outlet D to the diaphragm chamber in the radiator valve, 
keeping the valve closed. When the tube A contracts, due to a 
lowering of the room temperature, a downward force is exerted 
on the rod K and the block L, moving the valve lever to the right 
against the pressure of the spring N, and opening the valve 
G slightly. Because of the restricted passage at S.the air pressure 
in the passage Y and in the diaphragm chamber of the radiator 
valve, is lowered, allowing the latter to open and to admit some 




AUTOMATIC TEMPERATURE CONTROL 



167 



steam to the radiator. A further contraction of the tube A 
causes a further lowering of the air pressure at Y and an increase 
in the opening of the radiator valve. A thermostat of the posi- 
tive type is so constructed that an opening of the valve corre- 
sponding to G causes a complete reduction of the pressure at Y, 
allowing the radiator valve to open wide. 

149. Compressors. — The air supply is obtained from a small 
compressor, usually motor-driven, located in the basement. A 
storage tank is required and a constant pressure is maintained 
in the tank by means of a governor which automatically starts 




Fig. 116. — Compressed air thermostat-graduated type. 



carried 



and stops the compressor, as required. The pressure 
on the tank is usually about 25 pounds per square inch. 

The mixing dampers and the heating coils of a fan system can 
be readily controlled by thermostats, through the use of a dia- 
phragm motor as shown in Fig. 117. The control of humidity 
is also possible by the use of similar devices. These applications 
will be considered more fully under ''Fan Systems." 

150. Advantages of Automatic Control. — The advisability of 
installing a system of thermostatic control depends largely upon 
the type of building under consideration. The principal advan- 



168 HEATING AND VENTILATION 

tages of thermostatic control are the convenience and the in- 
creased comfort which it affords the occupants. Without any 
manipulation of the radiator valves, the temperature of the rooms 
is maintained at the most comfortable point, regardless of the 
outside temperature. In many cases a considerable saving in 
fuel can be effected by the use of automatic control, due to the 
fact that with manual control there is always a tendency for the 
rooms to become overheated through lack of attention to the 
radiator valves. This may be true even when graduated valves 
or other means of facilitating hand control are provided. The 



rr 




Fig. 117. — Diaphragm motor. 

actual amount of the saving in fuel is problematical, being given 
by many as from 10 to 30 per cent. In the average case it is 
probable that the lower figure is the more nearly correct. 

The objections to the compressed-air systems of thermostatic 
control are the rather high initial cost of the apparatus and the 
cost of maintaining and of keeping in adjustment the various 
parts of the system. Thermostatic control is especially desirable 
for hotels, schools, office buildings, and other buildings of a public 
character. For fan systems, automatic control of the dampers 
and coils is very much to be desired, and in most cases is abso- 
lutely necessary if satisfactory results are to be obtained. 



CHAPTER XII 
AIR AND ITS PROPERTIES 

151. Composition of Air. — The atmosphere of the earth is a 
mixture of several gases and vapors, the proportions of which 
vary somewhat in different locaHties and under different weather 
conditions. In general the proportions of nitrogen and oxygen, 
the two most important constituents of dry air, are approxi- 
mately as follows: 

By weight By volume 

Nitrogen 76.9 79.1 

Oxygen 23.1 20.9 

Carbon dioxide and water vapor are also contained in air in 
varying amounts and there are in addition small quantities of 
other gases, such as argon, ozone, and neon, which are of less 
importance. Air is not a chemical combination but is a mechan- 
ical mixture of these gases. 

152. Oxygen.^ — Oxygen, (O), which constitutes about one-fifth 
of the air by volume, is the element upon which animal life is 
dependent for its existence. In the process of respiration the 
lungs draw in and expel periodically a small quantity of air and 
a portion of the oxygen unites chemically, while in the lungs, 
with impurities of the blood, and thereby cleanses it. Some of 
the resulting products of this chemical reaction are exhaled in 
the form of gases and vapors. Our health and bodily comfort are 
dependent upon the proper performance of this process. 

153. Nitrogen. — Nitrogen, (N), which constitutes nearly all of 
the remaining four-fifths of the air by volume, is a relatively 
inert gas. It performs the important function of diluting the 
oxygen. As the human body is organized this dilution is essen- 
tial; an atmosphere of pure oxygen would soon burn up and 
destroy the body tissues. 

154. Carbon Dioxide. — Carbon dioxide, (CO 2), exists in small 
amounts in the open air, the purest air containing from 3 to 4 parts 
of CO2 by volume in 10,000. Carbon dioxide is also known as car- 
bonic acid gas, as it forms a weak acid when dissolved in water. 

169 



170 HEATING AND VENTILATION 

Being one of the products of respiration it is found in larger 
quantities in the air of occupied rooms. Carbon dioxide was 
for a long time believed to have a poisonous effect when taken 
into the lungs, but is now known to be quite harmless, of itself, 
even in appreciable amounts. It has the effect, however, of 
diluting the oxygen content of the air. This necessitates an 
increase in the rate of breathing and under extreme conditions 
causes great discomfort. Haldane and Priestly found that with 
2 per cent, of CO2 the lung action was increased 50 per cent.; 
with 3 per cent, of CO2 about 100 per cent.; with 4 per cent, of 
CO2 about 200 per cent.; and with 6 per cent, of CO2 about 500 
per cent. With 6 per cent, breathing becomes very difficult, 
while with more than 10 per cent, there occurs a loss of con- 
sciousness, but no immediate danger to life. Exposure to an 
atmosphere containing even 25 per cent, of CO2 does not result 
in immediate death. 

Being a product of respiration the amount of CO2 present in 
the atmosphere of a room is an indication of the amount of air 
being supplied to the room. The measurement of the CO2 
content of air is therefore of importance in ventilating work. 
There are several methods of measurement in use, the most 
accurate of which is that devised by Petterson and Palmquist. 
The apparatus is provided with a graduated chamber into which 
a sample of air is drawn and measured. It is then made to 
flow into a burette containing a saturated solution of caustic 
potash which absorbs the CO2. The air is then forced back to 
the measuring chamber and the decrease in volume noted. The 
apparatus is calibrated to read directly in parts per 10,000. 

Another method sometimes used is that of Wolpert. A solu- 
tion of sodium carbonate of known concentration is made up 
and a small quantity of phenolphthalein indicator is mixed with 
it. A suitable piston arrangement is used to force a known 
volume of the air to be analyzed into contact with the solution 
and the apparatus is shaken to promote the reaction between the 
acid CO2 and the alkaline solution. The process is repeated 
several times until the original pink color of the solution dis- 
appears. The number of charges of air necessary to cause the 
color change gives an indication of its CO2 content. 

155. Water Vapor. — Water vapor is an important constituent 
of the atmosphere. It is the most variable in quantity of 
any of the atmospheric elements, its amount depending largely 



AIR AND ITS PROPERTIES 171 

on the weather conditions. In the northern part of the United 
States the range of the moisture content of the atmosphere is 
very great. In New York, for example, it varies at different 
times from 0.5 grain to 7 grains per cubic foot. Water vapor, 
strictly speaking, is nothing other than steam at very low pressures, 
and its properties are similar to those of steam. This fact should 
always be borne in mind when dealing with the subject of atmos- 
pheric moisture. Another conception that should be thoroughly 
understood is that of Dalton's law of partial pressures. Accord- 
ing to this law, in any mechanical mixture of gases, each gas has 
a partial pressure of its own which is entirely independent of the 
partial pressures of the other gases. For example, consider a 
cubic foot of hydrogen gas at an absolute pressure of 5 pounds 
per square inch. If a cubic foot of nitrogen at an initial pressure 
of 10 pounds per square inch be injected into the same space, 
the resulting total pressure will be 15 pounds per square inch and 
the volume 1 cubic foot. In air, therefore, the oxygen, nitrogen, 
water vapor, and other gases each have their own partial pressure, 
the sum of all of them being equal to the total or barometric 
pressure. | 

For every temperature there is a corresponding partial pres- 
sure of water vapor at which the vapor is in a saturated state, 
its condition then being exactly similar to that of saturated steam, 
i.e., with the maximum number of molecules occupying a unit 
space. When the water vapor is in a saturated condition the air 
is also spoken of as being saturated since it then contains the 
maximum weight of vapor which it can hold at that temperature. 
If the temperature of the air is higher than that corresponding to 
the partial pressure of the water vapor, the vapor is superheated ; 
if the temperature drops below the saturation point some of the 
vapor is condensed and the vapor pressure is lowered to that 
corresponding to the new temperature. The saturation tem- 
perature is termed the dew point. The partial pressure of satu- 
rated vapor increases as the temperature increases. Conse- 
quently air at higher temperatures is capable of holding a greater 
weight of water per cubic foot. It should be remembered that 
the water vapor exists independently of the air except for the tem- 
perature effect of the latter; and the vapor may be thought of as 
occupying the given volume at its own partial pressure. The 
state of intimate mixture of the air and vapor causes their tem- 
peratures to be always the same. 



172 HEATING AND VENTILATION 

156. Relative and Absolute Humidity.^ — Atmospheric mois- 
ture is termed humidity. Absolute humidity is the actual 
vapor content expressed in grains per cubic foot or per pound 
of air. The ratio of the vapor content to the vapor content 
of saturated air at the same temperature, expressed in per 
cent., is called the relative humidity. For example, given a sam- 
ple of air at 70° having an absolute humidity of 4 grains per 
cubic foot. Since saturated air at 70° contains 8 grains per 
cubic foot, the relative humidity is 50 per cent. 

157. Total Heat of Air. — The total heat above 0° of air 
containing aqueous vapor is the sum of the heat of the air and 
the heat of the vapor. The latter has three components: the 
heat of the liquid, the heat of vaporization, and the superheat. 
In dealing with air containing vapor it is often convenient to use 
the units of weight instead of volume as a basis for calculations. 
The total heat above 0° in 1 pound of dry air at temperature ta 
is equal to 

H = C^ta - 0) 

in which ta is the air temperature and Cpa = 0.2415, the specific 
heat of air at constant pressure. 

Let Ww = the weight of water vapor contained in 1 pound of a 
mixture of air and water vapor. Then for saturated atmosphere 

H = {1- TFJ X C^aita - 0) + W^h' + r) 

in which h' = heat of the liquid above 0° for the water vapor. 

r = latent heat of the water vapor. 

For atmosphere below saturation at temperature ta 

H = {1-W^)X C^aita - 0) + W^{h' + r + Cpsita " t,)) 

in which td is the temperature at the dew point and C%, is the 
specific heat of water vapor at constant pressure. 

158. Adiabatic Saturation. — When air below saturation is 
brought into intimate contact with water there is always a 
tendency for some of the water to vaporize, adding to the mois- 
ture content of the air. If no heat is added from an outside 
source and none removed, the heat of vaporization for the mois- 
ture which is added will be supplied entirely at the expense of 
the heat of the air and of the superheat of the original quantity 
of water vapor. The process will continue until the saturation 
point is reached. A process of this nature taking place without 



AIR AND ITS PROPERTIES 173 

a transfer of heat to or from an outside source is called adiabatic 
and the final temperature which is reached is therefore termed 
the temperature of adiabatic saturation. Its depression below 
the original temperature of the air will depend upon the amount 
of moisture which was added to bring the air to saturation. 

The heat used in the vaporization of the moisture which was 
added is exactly equal to the heat given up by the air and by 
the water vapor which it contained originally, assuming that 
the water which was added was at the temperature of adiabatic 
saturation. The action may be expressed algebraically as 
follows:^ 

Let t = temperature of the air. 

t' = temperature of adiabatic saturation. 
W = weight of water vapor mixed with 1 pound of dry 

air at saturation at temperature t\ 
W = weight of water vapor mixed with 1 pound dry air 
at temperature t. 
W^ — W = weight of water added per pound of dry air. 
r = latent heat of vaporization at temperature t. 
Cps = specific heat of water vapor at constant pressure. 
Cpa = specific heat of dry air at constant pressure. 

(W - W)r = CpsWit - + Cpait - O (1) 

j,r rW - Cpajt - t') ,_, 

^= r + Cp.{t - O (') 

159. Measurement of Humidity. — The principle stated in 
the preceding paragraph affords a convenient means for 
measuring humidity, through the use of the wet- and dry-bulb 
thermometer. The instrument consists of two mercury ther- 
mometers, the bulb of one of which is covered with cotton wick- 
ing. The end of the wicking extends into a bottle of water and 
the entire length is kept wet by absorption. As the water is 
evaporated from the wicking its temperature is lowered to the 
temperature of adiabatic saturation or '^wet-bulb" temperature. 
By reading both thermometers when they have reached a con- 
stant point the wet-bulb depression is obtained and the moisture 
content of the air {W) can be found from equation (2), Par. 158. 

Distinction should be drawn between the wet-hulh temperature 
and the dew point, which was defined in Par. 155. The former 

1 From "Rational Psychroraetric Formulae" W. H. Carrier, Trans. 
A. S. M. E., 1911. 



174 



HEATING AND VENTILATION 



temperature is produced by adding moisture to the air and causing 
its temperature to drop by reason of the giving up of heat to 
vaporize the water. The dew point, on the other hand, is reached 
by removing heat from the air without changing its moisture 
content. In order to obtain accurate results it is necessary that 
the air surrounding the wet-bulb thermometer be in motion so 

that the maximum evaporation may be 
secured. For this reason the best form 
of wet- and dry-bulb thermometer is 
the ''sling psychrometer" illustrated in 
Fig. 118. In this instrument the wet- 
and dry-bulb thermometers are 
mounted on a metal strip pivotted to 
a handle. In using the instrument 
the wick surrounding the wet bulb is 
moistened and the instrument is whirled 
rapidly and read at intervals until there 
is no further drop in the wet-bulb tem- 
perature. Somewhat more accurate 
results are obtained with the ''aspira- 
tion" psychrometer in which a con- 
tinuous current of air is drawn over 
the wet-bulb thermometer by means of 
a small fan driven by clockwork. 
It is necessary that the water used 
III to moisten the wet bulb of the sling 

psychrometer be at approximately the 
wet-bulb temperature; otherwise the 
time required to bring the water to the 
wet-bulb temperature might be so great 
that parts of the wicking would become 
dry. The ideal psychrometric chart in 
Fig. 119 is constructed for use with the sling psychrometer.^ 
This chart gives the moisture content of air in grains per cubic 
foot, the volume basis being the more convenient for ordinary 
ventilating work. In Figs. I and II, in the Appendix, are given 
the. psychrometric charts which give the properties of air on the 
basis of 1 pound of air. 

160. Example of Use of Psychrometric Chart. — Given a 
dry-bulb temperature of 80° and a wet-bulb temperature of 70°, 

^ From "Fan Engineering," Buffalo Forge Company. 



i 




Fig. 118. — Sling psychro- 
meter. 



AIR AND ITS PROPERTIES 



175 



find the relative and absolute humidity and the dew point. 
From the 80° point on the horizontal scale follow the vertical 
line to its intersection with the diagonal line representing the 
wet-bulb temperature of 70°. ' Passing horizontally to the left 
from this point to the left-hand scale we find that the absolute 
humidity is 6.65 grains per cubic foot. To find the relative 
humidity we note that this same point lies between the 60 and 
70 per cent, relative humidity lines (the curved lines extending 



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20 25 30 35 40 45 50 55 60 G5 70 75 80 85 
Dry Bulb Temperature 

Fig. 119. — Psychrometric chart. 



95 100 105 



upward to the right) and that the relative humidity is 62 per cent. 
To find the dew point, follow left horizontally from this same 
point to the curved line of wet-bulb temperatures, called the 
saturation line. The dew point is 64.5°. 

The relation between the wet- and dry-bulb temperatures 
and the dew point should be thoroughly understood. 

161. Application to Air Conditioning. — If water is sprayed 
continuously into the path of a current of air and the same water 
is recirculated repeatedly the temperature of the water will 
approach the wet-bulb temperature of the air. The latter will 
not change but the dry-bulb temperature of the air will be lowered 
until it approaches the wet-bulb temperature, and at saturation 
the two will coincide. The wet-bulb temperature depends upon 



176 



HEATING AND VENTILATION 



the total heat of the air and vapor and will he constant so long as the 
total heat of the mixture of air and vapor is constant. In the process 
mentioned the heat of the air above the wet-bulb temperature 
and the superheat of its original water vapor content go to 
supply the heat of vaporization for the added moisture, as ex- 
pressed by equation (1), Par. 158. This means is often employed 
to cool the air for ventilation. 

If a spray of artificially cooled water be used the air can be 
cooled to within a few degrees of the water temperature. If this 
temperature is below the dew point of the air some of the moisture 
content will be condensed and the resulting condition will be one 



Table XXXVI. — Properties of Dry Airi 
Barometric Pressure 29.921 Inches 



Tem- 
per- 
ature, 


Weight 

per 
cu. ft., 
pounds 


Ratio 

to 
volume 
at 70° 

F. 


B.t.u. 
absorbed 
by 1 cu. 
ft. dry 
air per 
deg. F. 


Cu. ft. 
dry air 
warmed 
1° per 
B.t.u. 


Tem- 
pera- 
ature, 
deg. 
F. 


Weight 

per 
cu. ft., 
pounds 


Ratio 

to 

volume 

at 70° 

F. 


B.t.u. 
absorbed 
by 1 cu. 
ft. dry 
air per 
deg. F. 


Cu. ft. 
dry air 
warmed 
1° per 
B.t.u. 





1 1 
0.08636 0.8680 0.02080 


48.08 


130 


0.06732 


1.1133 


0.01631 


61.32 


5 


0.08544 0.8772 0.02060 


48.55 


135 


0.06675 


1.1230 


0.01618 


61.81 


10 


0.08453 0.8867 0.02039 


49.05 


140 


0.06620 


1 . 1320 


0.01605 


62.31 


15 


0.08363 0.8962 0.02018 


49.56 


145 


0.06565 


1.1417 


0.01592 


62.82 


20 


0.08276 0.9057 0.01998 


50.05 


150 


0.06510 


1.1512 


0.01578 


63.37 


25 


0.08190 0.9152: 0.01977 


50.58 


160 


0.06406 


1.1700 


0.01554 


64.35 


30 


0.08107 0.9246 0.01957 


51.10 


170 


0.06304 


1.1890 


0.01530 


65.36 


35 


0.08025 0.9340 0.01938 


51.60 


180 


0.06205 


1.2080 


0.01506 


66.40 


40 


0.07945 0.9434 0.01919 


52.11 


190 


0.06110 


1.2270 


0.01484 


67.40 


45 


0.07866 0.9530 0.01900 


52.64 


200 


0.06018 


1.2455 


0.01462 


68.41 


50 


0.07788 


0.9624 0.01881 


53.17 


220 


0.05840 


1.2833 


0.01419 


70.48 


55 


0.07713 


0.9718 0.01863 


53.68 


240 


0.05673 


1.3212 


0.01380 


72.46 


60 


0.07640 0.9811 0.01846 


54.18 


260 


0.05516 


1.3590 


0.01343 


74.46 


65 


0.07567, 0.9905 0.01829 


54.68 


280 


0.05367 


1.3967 


0.01308 


76.46 


70 


0.07495 1.0000 0.01812 


55.19 


300 


0.05225 


1.4345 


0.01274 


78.50 


75 


0.07424 1.0095 0.01795 

j 1 


55.72 


350 


0.04903 


1.5288 


0.01197 


83.55 


80 


0.07356 1.0190 


0.01779 


56.21 


400 


0.04618 


1.6230 


0.01130 


88.50 


85 


0.07289' 1.0283' 0.01763 


56.72 


450 


0.04364 


1.7177 


0.01070 


93.46 


90 


0.07222 1.0380 0.01747 


57.25 


500 


0.04138 


1.8113 


0.01018 


98.24 


95 


0.07157 1.0472 0.01732 


57.74 


550 


0.03932 


1.9060 


0.00967 


103.42 


100 


0.07093 1.0570; 0.01716 


58.28 


600 


0.03746 


2.0010 


0.00923 


108.35 


105 


0.07030, 1.0660 0.017C2 


58.76 


700 


0.03423 


2.1900 


0.00847 


118.07 


110 


0.06968! 1.0756 0.01687 


59.28 


800 


0.03151 


2.3785 


0.00782 


127.88 


115 


0.06908 1.0850 0.01673 


59.78 


900 


0.02920 


2.5670 


0.00728 


137.37 


120 


0.06848 1.0945 0.01659 


60.28 


1000 


0.02720 


2.7560 


0.00680 


147.07 


125 


0.06790 1.1040 0.01645 


60.79 


1200 


0.02392 


3.1335 0.00603 

! 1 ■ 


165.83 



From ''Fan Engineering," Buffalo Forge Company. 



AIR AND ITS PROPERTIES 



177 



of saturation at the final temperature. These principles are 
applied practically in the cooling and dehumidifying of air which 
will be discussed in Chapter XVI. 

162. Properties of Dry and Saturated Air.— The properties 
of dry air are given in Table XXXVI and the properties of 
saturated air in Table XXXVII, at the standard barometric 
pressure of 29.92 inches of mercury. 

Table XXXVII. — Properties of Saturated Airi 
Weights of Air, Vapor of Water, and Saturated Mixture of Air and Vapor at 
Different Temperatures, Under Standard Atmospheric Pressure 
of 29.921 Inches of Mercury 





Vapor pres- 
sure, inches 
of mercury 


Weight in a cu. ft. 


of mixture 


B.t.u. ab- 
sorbed by 

1 cu. ft. 
sat. air per 

deg. F. 


Cubic feet 


Temper- 
ature, 
deg. F. 


Weight of 
the dry- 
air, pounds 


Weight of 

the vapor, 

pounds 


Total weight 

of the 

mixture, 

pounds 


sat. air 
warmed 1" 
per B.t.u. 





0.0383 


0.08625 


0.000069 


0.08632 


0.02082 


48.04 


10 


0.0631 


. 08433 


0.000111 


. 08444 


. 02039 


49.05 


20 


0.1030 


0.08247 


0.000177 


0.08265 


0.01998 


50.05 


30 


0.1640 


0.08063 


0.000276 


0.08091 


0.01955 


51.15 


40 


0.2477 


0.07880 


0.000409 


0.07921 


0.01921 


52.06 


50' 


0.3625 


0.07694 


0.000587 


0.07753 


0.01883 


53.11 


60 


. 5220 


0.07506 


0.000829 


0.07589 


0.01852 


54.00 


70 


0.7390 


0.07310 


0.001152 


0.07425 


0.01811 


55.22 


80 


1 . 0290 


0.07095 


0.001576 


0.07253 


0.01788 


55.93 


90 


1.4170 


0.06881 


0.002132 


0.07094 


0.01763 


56.72 


100 


1.9260 


0.06637 


0.002848 


0.06922 


0.01737 


57.57 


110 


2.5890 


0.06367 


0.003763 


0.06743 


0.01716 


58.27 


120 


3.4380 


0.06062 


0.004914 


0.06553 


0.01696 


58.96 


130 


4.5200 


0.05716 


0.006357 


0.06352 


0.01681 


59.50 


140 


5.8800 


0.05319 


0.008140 


0.06133 


0.01669 


59.92 


150 


7.5700 


0.04864 


0.010310 


0.05894 


0.01663 


60.14 


160 


9.6500 


0.04341 


0.012956 


0.05637 


0.01664 


60.10 


170 


12.2000 


0.03735 


0.016140 


0.05349 


0.01671 


59.85 


180 


15.2900 


0.03035 


0.019940 


0.05029 


0.01682 


59.45 


190 


19.0200 


0.02227 


0.024465 


0.04674 


0.01706 


58.80 


200 


23.4700 


0.01297 


0.029780 


. 004275 


0.01750 


57.15 



163. Specific Heat of Air.- — The specific heat of a gas may be 
expressed in either of two ways: i.e., the specific heat of constant 

^From "Fan Engineering," Buffalo Forge Company. 

12 



178 HEATING AND VENTILATION 

pressure, and the specific heat of constant volume. The reason 
for this has already been stated (Par. 6). In ventilating work 
the former quantity is the one involved. Its value as determined 
by Carrier is 0.2415 B.t.u. 

Probl ems 

1. Given wet-bulb temperature 66°, dry-bulb temperature 80°. Find 
dew point, per cent, saturation, and moisture content. 

2. Given air at a temperature of 60° and containing 5 grains of water 
vapor per cubic foot. What is its relative humidity? 

3. The air outside of a building is at a temperature of 31° and has a rela- 
tive humidity of 84 per cent. On being drawn into the building it is 
heated to 70°. What is its relative humidity at the higher temperature? 

4. Air at 80° is 87 per cent, saturated. When cooled to 55° what is its 
new moisture content? 

5. Air at 25° has a humidity of 90 per cent. How much moisture must 
be added to give it a humidity of 50 per cent, when heated to 70°? 

6. A room has a volume of 1800 cubic feet. The air is changed once per 
hour. The incoming air has a temperature of 35° and a relative humidity 
of 75 per cent. It is desired to maintain a humidity of 50 per cent, in the 
room, the temperature being 70°. How many gallons of water must be 
evaporated in 24 hours to do this? 



CHAPTER XIII 
VENTILATION 

164. Ventilation Standards. — ^While the art of ventilating 
occupied rooms has advanced greatly during recent years, there 
are as yet no fixed standards as to what constitutes satisfactory 
ventilation. It is only very recently that many of the physio- 
logical effects of certain atmospheric conditions have been under- 
stood, and a satisfactory explanation of other phenomena is still 
lacking. The formulation of standard requirements has there- 
fore been very difficult and further progress now depends upon 
their establishment rather than upon the mechanical problems 
involved in fulfilling them. The most agreeable atmosphere that 
we know of is undoubtedly that which exists outdoors on a sunny 
spring day; but the specific qualities which make it agreeable 
have not been definitely discovered. It is well known, however, 
that many other things beside the mere supplying of a sufficient 
quantity of air are necessary to provide comfortable conditions. 

The effect of the atmospheric conditions upon the human body 
is twofold: namely, its effect upon the skin, and its effect when 
taken into the lungs. The former is largely a matter of removing 
heat from the body at the proper rate, while the latter is a ques- 
tion of supplying sufficient air of the proper cleanliness. 

In the maintaining of what is now considered as satisfactory 
ventilation, the following factors must be taken into account: 

1. Sufficient air supply, properly distributed. 

2. Reduction of odors and impurities. 

3. Removal of dust and bacteria to an acceptable amount. 

4. Proper temperature. 

5. Proper humidity. 

6. Proper amount of air motion. 

The first three of these factors concern the effect of the in- 
haled air, while the last three affect the rate of heat removal 
from the skin. 

165. Sources of Air Pollution. — The percentage of oxygen 
absolutely necessary for human existence has been shown, in 
the preceding chapter, to be quite low, and a considerable 
reduction of oxygen may take place without even causing great 

179 



180 HEATING AND VENTILATION 

discomfort. In general, it may be stated that the quantity of 
air to be suppHed for proper ventilation is governed by other 
factors which necessitate a greater quantity than that required 
to maintain a sufficient oxygen content. 

The air of occupied rooms becomes the recipient of many 
polluting elements, the most important of which are the products 
of respiration. The average person breathes at the rate of about 
17 respirations per minute while at rest. At each respiration, 
about 30 J-^ cubic inches of air are inhaled or about 18 cubic feet 
per hour, which amounts to about 34 pounds of air in 24 hours or 
a little over 7 pounds of oxygen. The inhaled air loses about 5 
per cent, of its oxygen content while in the lungs and gains 
from 3)-^ to 4 per cent, of carbon dioxide. The percentage com- 
position of free air and of expired air, by volume, is about as 
follows : 



Free atmosphere, 

per cent, 
(approximately) 



Expired air, 

per cent. 

(approximately) 



Oxygen j 20. 9 

Nitrogen 79 . 1 

Carbon dioxide ' . 03 to . 04 



15.4 

79.2 

4.03 to 4.04 



In addition to carbon dioxide, water vapor is an important 
product of respiration. The moisture thus added to the air will 
increase the humidity above the comfort point unless the atmos- 
phere is renewed with sufficient frequency. 

There are also emanations from the mouth, lungs, and skin 
which give rise to disagreeable odors and which are believed by 
some to have a poisonous effect when taken into the lungs. Al- 
though this behef is not universally accepted, and although the 
exact effect of this organic matter is not known, common clean- 
liness alone demands that sufficient fresh air be supplied to dilute 
such impurities considerably. 

There are other sources of air pollution, such as the products 
given off by the combustion in gas and oil lamps and from 
manufacturing processes. Gas lights give off carbon dioxide, 
water vapor, and traces of sulphuric acid. If the burners are not 
properly adjusted, carbon monoxide, which has a poisonous and 
sometimes a fatal effect, may also be generated. Table XXXVIII 
gives the amount of combustible consumed and the amount of 
carbon dioxide emitted per candlepower from gas lights. 



VENTILATION 181 

Table XXXVIII. — Am Pollution by Gas Lighting 



Consumption of combustible 

per candlepower in cubic 

feet per hour 



Carbon dioxide per candle- 
power in cubic feet per 
hour 



Fishtail burner . . 
Argand burner. . , 
Welsbach burner 



0.802-0.527 
0.0 -0.445 
0.053-0.024 



0.494-0.304 

0.254 
0.030-0.057 



Manufacturing and chemical processes give off various gas- 
eous impurities, but such conditions require individual study 
and no set rules can be given. 

166. Amount of Air Required. — The proper amount of air 
supply has been determined from experience for different classes 

Table XXXIX. — Air Supplied to Various Classes of Buildings 



Cubic feet per hour 
per occupant 



No. of renewals 
of air per hour 



Churches, auditoriums and assembly rooms 

Theatres 

Grade schools 

High schools 

College class rooms 

Hospitals for ordinary diseases 

Hospitals for children 

Hospitals for contagious diseases 

Hospitals for wounded 

Barracks 

Living rooms in residences 

Stairways and halls 

Bedrooms 

Work shops 

PubUc waiting rooms 

Pubhc toilet rooms 

Small convention halls 

Greneral offices 

Private offices 

PubUc dining rooms 

Banquet halls 

Basement restaurants 

Hotel kitchens 

Public libraries 

Textile mills 

Engine rooms 

Boiler rooms 

Railroad roundhouses . . . 



1,200-1,800 
1,000-1,200 
1,000-1,500 
1,200-1,800] 
1,500-2,000 
2,500-3,500 
2,000-2,500 
5,000-5,500 
3,500-5,000 
1,000-1,800 

1,200 
600 

1,000 
600-2,000 



1-2 

3^-1 

4 
10 

4 

3 

4 

4 

5 
8-12 
4-6 

3 

4 
3-6 
2-6 

12 



182 HEATING AND VENTILATION 

of buildings. For buildings such as theatres and schools, it is 
customary to provide a certain volume of air per minute for each 
occupant. For rooms where the number of occupants is vari- 
able or where there is pollution from sources other than respira- 
tion, sufficient fresh air is provided to renew that in the room a 
certain number of times per hour. For ordinary conditions of 
temperature and humidity, Table XXXIX gives the usual 
practice as to the amount supplied. 

167. Methods of Measuring Air Supply. — When the air enters 
a room through but one or two ducts, the quantity can be 
directly measured by a pitot tube or anemometer, the use of 
which will be discussed in Chapter XV. Another method which 
in many cases is more convenient is based on the measurement 
of the carbon dioxide content of the air combined with our 
knowledge of the rate at which the carbon dioxide is added by 
the exhalation from the occupants. 

Let y = volume of air admitted to the room in cubic feet 

per hour. 
a = volume of CO2 contained in a unit volume of the 

air admitted, 
ri = amount of CO2 per unit volume of air in the room 

at the beginning of the test. 
r2 = amount of CO2 per unit volume of air in the room 

at the end of the test. 
r = amount of CO2 per unit volume of air in the room 

at any time during the test. 
R = volume of room in cubic feet. 
c = amount of CO2 produced in the room, in cubic 

feet per hour. 
t = time of experiment in hours. 

During any small period of time dt, the amount of air enter- 
ing the room is Vdt and the amount of CO2 contained in the 
entering air is aVdt. The amount of CO2 produced during 
the time dt is cdt. During the same interval, an equal volume 
Vdt leaves the room through the exhaust flues and its CO2 
content is rVdt. The net increase in the volume of CO2 in the 
room is then 

(aV + c)dt - rVdt = (aV - rV + c) dt 

Let the increase in the CO2 content of the air in the room per 



VENTILATION 183 

cubic foot during the interval di be represented by dr. Then the 
total net increase is Rdr. Equating the two 

Rdr = {aV - rV + c)dt (1) 



and 



(aV + e) — Vr 



if. 

Jn a 



V -\-c- Vr 



t = R\^ log, {aV + c- Vr) 

|ri V 

, R, Vn- aV - c 

^ = 2.303 flog.o l;iZ:lZl (3) 

If ri = r2, which means that there is no increase in the CO2 
content of the air in the room, then the amount entering the 
room, plus the amount produced must equal the amount leaving 
the room, or 

aV -j- c = Vr2 
from which 

c c 

and r2 = ri = a + ^ (4) 



r2 — a V 

If c = 0, then from (3) V = 2.303 f logio ^^"-^^ (5) 

Equation (4) is applied practically by assuming a certain 
production of CO2 per hour per person, which figure is usually 
taken as 0.6 cubic foot. Equation (4) then becomes 

- «■ = ^. »> 

in which 

C.F.H. = cubic feet of air per hour supplied to the room 
per occupant. 
CO2 = carbon dioxide content of the room air in parts 
per 10,000. 
X = carbon dioxide content of the outside air in 
parts per 10,000. 

This formula is recommended by Dr. E. V. Hill and is used by 
the Health Department of the City of Chicago. The chart in 



l84 



HEATING AND VENTILATION 



Fig. 120 shows the air supply per person when any given CO2 
content exists in the room. The above method of determining 
the air supply does not apply when there is any source of carbon 
dioxide other than the lungs of the occupants. 

168. Air Distribution. — Merely to supply enough air to a room 
is not sufficient for good ventilation; it must be distributed in 
a fairly uniform manner so that each occupant receives approxi- 
mately the specified amount. The methods of distribution will 
be dealt with later. To determine the uniformity of distribu- 
tion, the common method is to take measurements of the CO2 con- 
tent in different parts of the room and thus determine the varia- 
tion of the quantity supplied per occupant at the different 
points from the average quantity. 

c 3,000 



<^! 2.500 



M 2.000 



S 1,500 

1 

^ 1.000 



^ 500 



100 







































Formula CO 2 
TransDosed V 


6000 


-+x 


CFH per occupant 


\ 












X may be taken as 4 if an analysis 
of outeide air is not made 


\ 


























V 




























^-— 


■ — . 


















J 5 10 15 20 25 30 35 40 45 50 55 60 65 

CO2 Content in 10,000 Parts of Air 

Fig. 120. — Chart showing air supply per person for various amounts of Co2- 



169. Temperature and Humidity. — One of the chief objects 
sought when air for ventilation is provided is the establishment 
of such conditions that heat will be removed from the human 
body at a rate which is favorable for comfort and health. Heat 
is lost from the body in three ways : by radiation, by convection, 
and by the evaporation of moisture from the skin. A relatively 
large amount of heat is lost by convection and consequently 
the temperature of the surrounding air and the amount of air 
movement are important factors. 

The amount of heat lost due to the evaporation of perspira- 
tion from the skin depends upon the relative humidity of the air 
and upon the amount of air motion. It is also dependent, of 
course, upon the amount of perspiration which is given off by 



VENTILATION 



185 



the pores of the skin, more heat being lost by evaporation from 
the skin of a person who perspires freely than from a dry skin. 
Comfortable conditions can exist through a rather wide range 
of temperature and relative humidity provided that the combina- 
tion of the two is such as to cause the proper rate of heat loss from 
the body. The air motion may also vary, but within rather 
narrow limits. 

The chart in Fig. 121 showing the proper relation between the 
temperature and humidity was constructed by Dr. E. V. Hill 
from a series of tests made by Prof. J. W. Shepherd. From the 
center line of the ''Comfort Zone" shown in the chart, it will be 
noted that equally comfortable conditions can be had with a 



75 
73 

71 


.^ 


^==: 





















































^ 















^ 






























■■~~~ 


fi""" 


"sTc" 












-^ 


^_ 












— 


■— 


— — 


v< 


ity 


p;aL 




^ 


^^ 




-^r 




-> 


...^^ 










■^ 


-- 


, 


Ibo 


iW^ 


rrti 










— 


-^ 


^^07 




















*"*• 


-^ 




>tie 


Of 


^o^ 








— 


~— 


---. 


. 




2 65 

a 


^- 


-^ 
















T^ 











fe 


















2 tj-i 
§61 
^59 

57 






















W 


• 


'^ 


"-- 


.^ 








~-~- 


-^ 


^ 




















7', 


>oc 




-^ 















^ 


^ 








*"■ 


■^•^ 


-. 


























' - 


-^ 


^ 








"-^ 




■^ 








































"^ 


-- 


^i^ 






"\ 


^ 





30 32 34 



Fig. 121. 



40 42 44 46 48 50 52 54 56 58 60 62 64 
Relative Humidity Per Cent 



70 72 74 76 78 



Comfort Zone" showing the temperature and humidity required 
to produce comfortable conditions. 



temperature of 65° and a humidity of 56 per cent, as with a tem- 
perature of 70° and a humidity of 36 per cent. Low humidities 
such as ordinarily exist in most buildings during the heating 
season are known to be detrimental to health, as the membranes 
of the throat and nose become dry and irritated. There is Uttle 
doubt but that the proper humidification of the air of residences 
and other heated buildings is very beneficial from a physiological 
standpoint but there have been certain difficulties in the way of 
its universal application. Many of the devices intended for the 
purpose are entirely inadequate to supply the moisture required 
by even a moderate-sized room. There is also a general lack of 
appreciation of the quantities of moisture required, some idea 
of which was brought out in the preceding chapter. Another 
drawback is the tendency for moisture to be deposited on the 



186 HEATING AND VENTILATION 

windows when even a moderate humidity is maintained in very- 
cold weather. For these reasons, the appUcation of artificial 
humidity has been limited to buildings of sufficient size and of 
such a character as to make practicable the use of an air washer 
or other rather elaborate means for humidification. 

Excessive humidity, on the other hand, is undesirable, as it 
causes a feeling of intense discomfort, especially when accom- 
panied by high temperature, because of its effect in lowering the 
rate of evaporation from the skin and therefore retarding the 
process of heat removal from the body. According to Prof. 
Foster, about 4 pounds of water are given off by an adult man 
under extreme conditions in 24 hours, of which 2J^ pounds are 
evaporated from the skin and the remainder is contained in the 
expired air. Under average conditions, the amount given off is 
about one-half the above. The heat given off from the body 
will vary from about 335 to 460 B.t.u. per hour depending upon 
the age, sex, diet, amount of exercise, etc. About 15 B.t.u. 
of this amount are given off with the expired air and 35 B.t.u. 
are contained in the moisture with which the expired air is 
saturated. Approximately 70 B.t.u. are contained in the mois- 
ture which is evaporated from the skin, leaving about 250 B.t.u. 
to be lost by convection and radiation. The last two quantities 
especially are extremely variable under different atmospheric 
conditions. In a hot, dry atmosphere, for example, the air 
temperature may be higher than that of the body and no heat 
can be given off by convection or radiation. The evaporation of 
perspiration from the skin must then be depended upon to remove 
all of the excess heat from the body. 

In crowded rooms, the heat and moisture given off from the 
bodies and from the exhalations of the occupants may render the 
atmosphere extremely uncomfortable, so that cooling and de- 
humidifying are required. It has been demonstrated repeatedly 
that the depressing effect of a so-called stuffy atmosphere is due 
to its action on the skin as much as or even more than to its effect 
on the lungs. 

When the air is artificially cooled, it has been found that the 
inside temperature must be raised somewhat as the outside 
temperature increases, so that the shock to the sensations of one 
entering from the outside will be minimized. The inside tem- 
perature should not be more than 10° or 12° below the outside, 
as a^maximum. 



VENTILATION 187 

170. Air Moveme,'nt. — The rate of evaporation of moisture 
from the skin depends, in addition to the temperature and 
humidity of the atmosphere of the room, upon the continuous 
renewal of the aerial envelope surrounding the body. Unless 
this renewal takes place, the air immediately surrounding the 
body increases in temperature and moisture content to such an 
extent that the skin evaporation is retarded to an uncomfortable 
degree. A proper circulation of the air within a room also pre- 
vents the immediate reinspiration of the air expired from the 
lungs and diffuses it throughout the room. The motion of the 
air, however, should never be such as to cause uncomfortable 
drafts. In general, a movement toward the face is greatly 
preferable to one from the rear. An air movement of about 2 
feet per second is considered to be permissible, but a much 
greater velocity is uncomfortable. Air movement may be 
directly measured by injecting into the air clouds of smoke and 
timing their movement across the room. Toy balloons are also 
used for this purpose. 

Cubic space is an important factor in ventilation, particularly 
in crowded rooms, for with too small a volume per person it 
may be impossible to move the required amount of air through 
the room without giving rise to unpleasant drafts. Dr. Billings 
recommends the following as the minimum amount of space to 
be allowed per occupant. 

Lodging or tenement house . . 300 cubic feet per person 

School room 250 cubic feet per person 

Hospital ward 1,000-1,400 cubic feet per person 

Auditoriums 200 cubic feet per person 

In computing the cubic space for this purpose, all space over 
12 feet above the floor should be neglected. 

171. Odors. — Another function of ventilation is the removal 
or reduction of odors, the most common and most objectionable 
of which arise from the bodies of the occupants. The sources 
of these odors are emanations from the throat and lungs, the 
perspiration from the skin, and soiled clothing. In factories, 
odors are created by industrial operations of various sorts. 

The so-called '^ crowd smell" is not harmful of itself, for it 
has been shown that healthful existence is quite possible in such 
an atmosphere. Repulsive odors are indirectly harmful, how- 
ever, in that they cause the occupants of the room to breathe 



188 HEATING AND VENTILATION 

less deeply; but regardless of their actual physiological effect, 
modern standards of cleanliness require that sufficient air be 
supplied to occupied rooms to maintain a wholesome atmosphere. 
As yet, no satisfactory standard has been found for the meas- 
urement of odors. 

172. Ozone. — Ozone is used to some extent as a means for 
counteracting odors and bacteria. Ozone is simply a form of 
oxygen in which the molecule consists of three instead of two 
atoms. The additional atom is readily liberated and the sub- 
stance is consequently an active oxidizing agent. Ozone is 
present in very minute amounts in the atmosphere. 

When injected into the atmosphere of a room with a con- 
centration of not more than 1 part per million, ozone is capable 
of obliterating even very marked odors. The exact action which 
takes place is at present a matter of debate. By some it is 
believed that ozone actually destroys the odors through its 
oxidizing action. It is known, however, that it is quite possible 
to compensate one odor with another so that its effect upon the 
olfactory membrane is neutralized, and it may be that the real 
action of the ozone is a masking of the odors- by what is called 
''olfactory compensation" rather than a destroying of them. 

It is very essential that the concentration of the ozone be 
kept very low, for in an atmosphere of more than about 1 part 
per million of ozone, serious irritation of the throat and lungs is 
liable to result. 

The common method of producing ozone is by means of an elec- 
trical discharge at high voltage. Several commercial machines 
are available for the purpose. 

173. Dust and Bacteria. — The air, especially that of cities, 
contains a large amount of dust in very finely divided particles. 
These particles consist of many different substances, most of 
which are mineral. In large cities, tons of cinders and smoke 
particles are cast out into the air annually, which adds to the 
production ■ of dust from other sources. Dust in itself is not 
particularly injurious to health but it serves as a carrying me- 
dium for all sorts of bacteria. 

Several methods of determining the dust content of air have 
been devised. The most successful scheme is to draw a sample 
of air into a suitable cyhnder containing a glass disc coated with 
an adhesive varnish and so placed that the indrawn air impinges 
upon it. The number of dust particles determined by microscopic 



VENTILATION 



189 



count affords an indication of the amount of dust in the air. 
Dust can be quite thoroughly removed from air by means of the 
air washer, to be described later. 

174. Methods of Introducing Air. — In providing ventilation for 
a room, it is necessary to adopt a definite scheme for the intro- 
duction of fresh air and the removal of the vitiated air. When 
the air quantities are small the leakage around the windows may 
be relied upon as a means for permitting the escape of the air, 
but in general, it is necessary to install a system of vent flues. 

There are two general methods of circulating the air through a 
room. In the upward system, the air is introduced through the 
floor or through the side walls near the floor and is removed near the 




Fig. 122. — Effect of various locations of inlet and outlet. 



ceiling. In the downward system, the air is introduced through 
registers in the side walls located from 7 to 10 feet above the floor 
and is removed near the floor. The former method is especially 
adapted to theatres and auditoriums where a large number of 
small openings can be provided in the floor, thus securing a very 
even distribution. The upward system is also suitable for 
restaurants and rooms where there is smoking or where other 
impurities or odors are created which have a natural tendency 
to rise. The downward system is used in schools, hospitals, etc. 
where the occupants are not many and- where it is not practicable 
to have openings in the floor. 

The relative location of the inlet and outlet openings greatly 



190 HEATING AND VENTILATION 

affects the thoroughness of the air renewal throughout the room. 
It has been demonstrated that the most effective scheme is to 
place the outlet near the floor and on the same side of the room as 
the inlet. The effects of various locations of the inlet and outlet 
are shown in Fig. 122. 

Problems 

1. A test made in a room in which there are several people shows a CO2 
content of 12 parts per 10,000. What quantitj^ of air is being supplied per 
hour per occupant? 

2. A test of the air of an occupied room shows a CO2 content of 13 parts 
per 10,000. Outside air contains 3}i parts per 10,000. How much air is 
being supplied per hour per occupant? 



CHAPTER XIV 
HOT-AIR FURNACE HEATING 

175. Furnace Systems. — The hot-air furnace is widely used 
throughout the country in the heating of residences of moderate 
size. In addition to its simpUcity and relatively low cost, it 
has the great advantage of providing fresh air for ventilation. 
It is especially well adapted to moderate climates where, for a 
large part of the winter, heat is needed only in the morning and 
evening. 

As brought out in Chapter III, the greatest disadvantage in a 
furnace system is the fact that the force producing circulation, 
being dependent upon the relatively slight difference in density 
between the heated and unheated air, is quite small and is often 
insufficient to overcome the resistance of the piping or the pres- 
sure of a very strong wind blowing against the building. These 
difficulties can often be overcome, however, by intelligent design 
of the system. The size of the building which a hot-air furnace 
can serve is limited because of the friction in the horizontal 
piping. The practical limitation to the length of horizontal 
ducts which can convey the required volumes of air is about 20 
feet. It is sometimes feasible to install two separate furnaces 
and thus avoid pipes of excessive length. 

There are many forms of furnaces on the market, some of 
which are of indifferent design and workmanship. The non- 
success of many furnace installations is usually due to this 
fact and to .the lack of intelligent planning of the piping system. 
A common mistake, brought about by the endeavor to minimize 
the cost of the installation, is the use of a furnace of insufficient 
size. As a result, a very hot fire must be maintained and the 
flue gases leave the furnace at a high temperature, necessitating 
the use of an excessive amount of fuel. 

In a furnace system the heat is absorbed by the air as it passes 
through the furnace and is carried by the air to the rooms above. 
The air circulates through the rooms, giving up heat to the 
objects in the room and to the walls. The walls and the con- 

191 



192 HEATING AND VENTILATION 

tents of the room remain at a slightly lower temperature than the 
air. If no foul-air flues are provided, the air entering the room 
must eventually find its way out through the cracks around the 
windows, through the walls themselves, or through the doors into 
other rooms; for otherwise the flow of air into the room could not 
be maintained. It sometimes happens, in a tightly constructed 
building, that this leakage is insufficient, and the flow of air to 
the room is retarded. A foul-air flue from each room is there- 
fore desirable, although in the average residence its initial cost is 
seldom deemed warranted. 

The air entering the furnace may come either from outside or 
may be partially or wholly re-circulated from the house. It is 
best to provide both means of air supply, so that either may be 
used as conditions demand. When only a few people are in the 
building, the air may be re-circulated, but for a number of people 
it is very desirable that an ample supply of fresh air be introduced. 
The economy of a hot-air system is affected by the proportion of 
the air taken from each of these sources. When all the air is re- 
circulated from the house, then the economy of the hot-air 
furnace is about the same as that of a steam or hot-water plant ; 
but when air is taken from outside, then a certain amount of heat 
is used in warming it up to the temperature of the room, and this 
heat is not available for supplying the heat losses from the build- 
ing. But heat used in this way should be considered as the 
price of ventilation and should not be charged against the effi- 
ciency of the system. 

176. Furnaces. — The hot-air furnace consists fundamentally 
of a firepot and a series of passages for the flue gases, surrounded 
by a metal or brick casing. The air circulates through the space 
between the furnace proper and the casing, absorbing heat from 
the hot surfaces of the firepot and gas passages. The gas pas- 
sages are usually formed by a simple casting called a '^radiator." 

Hot-air furnaces are quite varied in design. In general there 
are two types: those with the radiator at the top of the furnace, 
as in Fig. 123; and those with the radiator near the bottom of 
the furnace, as in Fig. 124. • Occasionally, in cheap furnaces, 
the radiator is left off entirely. For the best possible efficiency 
in any furnace the entering air should first come into contact 
with the surfaces behind which are the coldest flue gases and the 
air leaving the furnace should pass over the hottest surfaces. 
This ideal condition is difficult of realization, for mechanical 



HOT-AIR FURNACE HEATING 



193 




Fig. 123. — Furnace with radiator at the top (casing removed). 




Fig. 124. — Furnace with radiator near bottom (casing removed). 
13 



194 HEATING AND VENTILATION 

reasons, but the furnace which most nearly approaches it will 
in general be the most efficient. 

The heating surfaces of a furnace may be divided into two 
classes: (a) direct heating surfaces, which are those which are 
in contact with the fire or which receive heat by direct radiation 
from the fire; and (6) indirect heating surfaces, which are heated 
only by the hot gases. In addition there are some surfaces 
which receive heat only by conduction from the heating surfaces 
proper, such as projections and braces, these being called ''ex- 
tended" surfaces. The parts of such surfaces which are more 
than about 2 inches from actual heating surface are of doubtful 
effectiveness, however. 

All of the heating surfaces give up heat to the air entirely by 
convection. The amount of heat transmitted through the heat- 
ing surfaces of course increases as the difference in temperature 
between the air and the products of combustion increases. The 
effectiveness of the heating surfaces decreases as the distance 
from the fire increases and direct heating surfaces are naturally 
more effective than indirect heating surfaces. The more rapid 
the flow of air over the heating surfaces, the greater will be the 
amount of heat removed. 

Since the effectiveness of the heating surfaces depends upon 
the design of the furnace, it is impossible to base the capacity 
of the furnace upon the amount of heating surface. Roughly, 
however, the heat transmission may be assumed to be, on an 
average, from 1000 to 1500 B.t.u. per hour per square foot of 
surface. 

177. Furnace Construction. — The firepot and radiator are 
usually made of cast iron, although steel is sometimes used. 
There is no appreciable difference in the thermal conductivity 
of the two materials. It is essentialthat the joints between the 
different castings be air-tight so that the products of combustion 
cannot escape and be carried to the rooms above. The joints, 
therefore, are of a modified tongue and groove design, the grooves 
being filled with a special cement and the castings drawn and held 
together with draw bolts. Joints should be as few as possible 
and vertical joints should be avoided. 

The firepot is usually sUghtly conical and should be deep 
enough to contain sufficient coal to last for 8 hours, leaving 
enough unburned coal on the grates at the end of that time to 
ignite the fresh charge of fuel. With hard coal this means that 



HOT-AIR FURNACE HEATING 195 

the depth should be sufficient to allow for 50 pounds of coal 
being placed on the grate per square foot of grate. Coke or 
soft coal will require a greater depth of firebox than anthracite 
coal. The grate area should be from 1 :25 to 1 : 12 of the area 
of the heating surface, the proportion depending upon the kind 
of fuel and the size of the furnace — the larger the furnace, the 
smaller the ratio. If anthracite coal is used the ratio should 
not exceed 1 :25. If bituminous coal is used it should be 1 :20 
and for coke about 1 : 15 for furnaces of average size. 

For burning soft coal some furnaces are provided with an 
auxiliary air supply so arranged that heated air is introduced 
into the firepot above the fuel bed, mixing with the combustible 
gases and promoting complete and smokeless combustion. 

The furnace casing is usually of galvanized iron, although 
large furnaces are sometimes enclosed by brickwork. When a 
galvanized-iron casing is used, insulation is obtained by providing 
an inner casing of black iron or tin with an air space between 
the inner casing and the outer casing of about 1 inch. The 
area between the furnace and casing should be sufficient so that 
no appreciable resistance is interposed to the circulation of air 
through the furnace. In small furnaces the velocity should not 
exceed 250 feet per minute and in larger furnaces 300 to 250 feet 
per minute. These figures apply only to gravity circulation. 

Furnaces are rated by the manufacturers either upon a basis 
of the volume of the building to be heated or upon the total 
cross-sectional area of the warm air ducts. Inasmuch as these 
ratings usually represent about the maximum capacity of the 
furnace, it is well to choose a furnace of 25 to 50 per cent, excess 
capacity. 

178. Humidification. — The hot-air furnace system affords a 
particularly favorable opportunity for humidification, but unfor- 
tunately most of the manufacturers have been extremely backward 
in providing adequate apparatus for adding the necessary amounts 
of moisture to the air. Most furnaces are equipped with some 
sort of a ''water pan" which is usually installed near the bottom 
of the furnace. This location is entirely wrong, for the air as it 
enters at the bottom of the furnace has the least capacity for 
absorbing moisture. To be effective, the humidifying apparatus 
should be placed where the hottest air will pass over it, i.e., at 
the furnace outlet. Few realize that in order to maintain a 
proper humidity in even a small house there must be evaporated 



196 HEATING AND VENTILATION 

hourly a quantity of water of the order of 10 pounds. To be 
satisfactory, the water pan must therefore be kept filled auto- 
matically from the water-supply system. Fig. 125 shows a 
humidifier which is located at the top of the furnace and is 
automatically filled. The amount of water evaporated increases 
with the amount of air passing through the furnace and with the 
temperature of the air, making the apparatus to some extent 
self-regulating. Accurate automatic regulation is impossible, 
however, without a system of humidity control such as will be 
described later. 




Fig. 125.— Humidifier. 

179. Cold-air Pipe. — The air supply to the furnace may be 
taken from outside or can be re-circulated from the house. It 
is also quite feasible to take only a certain amount of air from 
outside and to supply the remainder by re-circulation. With 
complete re-circulation the advantage of ventilation is entirely 
lost but the system is somewhat more economical. The cold- 
air duct may be of galvanized iron or may be constructed of 
tile and placed beneath the basement floor. It should come from 
the side of the house which is subject to the prevailing winds. It 
is sometimes desirable to have cold-air ducts leading to different 
sides of the house so that the supply of cold air may be taken 
from the windiest side. The cross-section of the cold-air duct 
should be 80 per cent, of the aggregate area of the supply ducts 
leaving the furnace. 

The re-circulating duct should be brought from the coldest 
part of the house and from some room such as the hall which 
has other rooms leading into it. The side of the stairway^ the 
lower stairway risers, or the space in front of large windows are 
good locations for the re-circulating register. 

If it is desired to re-circulate partially and to take the balance 
of the air from outside, the re-circulating pipe should be brought 
to the furnace independently of the fresh-air pipe, and a deflect- 
ing plate placed in the air space under the furnace. If this 
is not done, the air may come in from the outside and pass up 



HOT-AIR FURNACE HEATING 197 

the re-circulating pipe instead of through the furnace. Both 
the fresh-air pipe and the re-circulating pipe must be provided 
with dampers. 

It is a common error to make the re-circulating pipe of a 
furnace system too small. The area of the re-circulating pipe 
should be not less than three-fourths the combined area of the 
hot-air pipes, and it is better to have it equal to their combined 
area. 

180. Hot-air Pipes. — The furnace should be centrally located, 
or if the coldest winds come from a certain direction, it can be 
located toward that side of the house. The pipes leading from 
the furnace should be as short and direct as possible; long hori- 
zontal pipes should be avoided. 

The horizontal pipes are called leaders; the vertical pipes 
flues or risers. Leaders are usually made of round pipe. All 
leaders should be given the same pitch of at least 1 inch per foot 
and should leave the furnace at the same elevation. They should 
be insulated with asbestos paper, or if extending through a very 
cold part of the basement, with an air-cell covering. It is desir- 
able to provide a damper in each pipe so that the distribution 
of the air among the different rooms can be adjusted. The 
risers should in every case be installed in an inside partition, 
as the cooling effect, when placed in an outside wall, would 
greatly retard circulation, besides causing an excessive waste of 
heat. It is usually necessary to limit the depth of the riser to 
4 inches, so that it may be enclosed in the studding. The width 
also is sometimes limited by the distance between the studding 
and many furnace systems suffer from this source. It is some- 
times necessary to run two risers to large second-floor rooms 
when space is not available for a single riser of sufficient size. 
Architects often fail to realize the importance of providing suf- 
ficient space for this purpose. 

Risers, when made of single-walled pipe must be insulated with 
asbestos paper to protect the woodwork and a clearance on all 
sides of at least 3^ inch must be left. Double-walled pipe 
which has an air space between the walls is becoming widely used. 
The air space serves as an insulator and greatly decreases any 
possible fire hazard as well as reducing heat loss from the pipe. 
When double-walled pipe is used the proper size should be selected 
so that the net inside area will not be reduced below the computed 
requirements. Bright tin is ordinarily used for all piping. 



198 



HEATING AND VENTILATION 



The leader is connected to the riser by means of a fitting 
called a ''boot" shown in Figs. 126a and 126Z>. The form shown 
in Fig. 126a is preferable as it interposes less resistance to the 
flow of air. 

The air is delivered into the room through a register of the 
form shown in Figs. 127 and 128. Floor registers have the advan- 
tage that they may be made of any size and may be placed in 
any part of the room. They are often favored because the air 





v'a 




Fig. 126a.— Boot of im- 
proper design. 



Fig. 1266. — Boots of good design. 



leaving them does not deposit dust on the walls as does the side- 
wall register. Floor registers, however, are very insanitary as 
they collect great quantities of dirt; and they also frequently 
necessitate cutting the carpets or rugs. On the whole, the side- 
wall register is much to be preferred. Registers are provided 
with means of cutting off the flow of air in the form of louvres or, 




Fig. 127. — Floor register. 



iDEinnDonnnn 

ESnBDDDDnH 

EnnanHBBNN 
MonnQoBn 



Fig. 128. — Wall register. 



in the side-wall type, a single shutter of sheet metal. The 
shutters in some of the registers should be omitted, so that by no 
possible chance could all of the air supply be cut off; for with no 
air circulating through the furnace, the danger of overheating 
and burning out the firepot is great. It is often convenient to 
supply a first-floor register and a riser from a single leader. This 
can be very satisfactorily accomplished by means of the arrange- 
ment shown in Fig. 129. The free area of an ordinary register 



HOT-AIR FURNACE HEATING 



199 



is only about half of its gross area and its size must therefore 
be about double that of the pipe which supplies it. For a floor 




Fig. 129. — Method of connect- 
ing first floor register and riser to 
a single leader. 



Fig. 130. — Box for floor register. 




Fig. 131. — Stack and register frame — double walled pipe. 

register a box of the form shown in Fig, 130 is provided and for 
a wall register a frame of the form shown in Fig. 131 is used. 

Fig. 132 shows the general arrangement of a furnace system. 

181. Size of Hot-air Pipes. — There are two methods of 



200 



HEATING AND VENTILATION 



figuring the size of the hot-air pipes, the B.t.u. method and the 
volume method. The former is the more rational and is the one 
recommended. 

Example of B.t.u. Method. — Assume that the heat loss from 
the given room is 12,000 B.t.u. per hour and that the air enters 
at 140°, room temperature being 70°. Each cubic foot of air 
entering the room will give up enough heat to Jower its tem- 
perature from 140° to 70°. The amount of heat given up 
when a cubic foot of air is cooled 1° is approximately ^^5 B.t.u. 



Wl^^^JI 




Fig. 132. — General arrangement of furnace system. 

Therefore, the heat given up per cubic foot is — ^ — = 1.27 B.t.u. 

The volume of air required per hour = 12,000 -^ 1.27 = 9460 
cubic feet. Allowing a velocity of 250 feet per minute in the 

hot-air pipe, the required area of the hot-air pipe is ocn v fin 

= 0.63 square foot. 

The velocity of air for first-floor leaders may be taken as 3 
to 4 feet per second, for second-floor leaders 4 to 5 feet per second, 
and for third-floor leaders 5 to 6 feet per second. The risers 
leading to second- and third-floor rooms may have a velocity as 
high as 400 feet per minute. 

Registers should be proportioned so as to give a velocity of 
2 to 3 feet per second on the first floor and 3 to 4 feet per second on 
the floors above, on the basis of the effective area of the register. 

Volume Method. — In the volume method the area of the hot- 




HOT-AIR FURNACE HEATING 



201 



air pipe is assumed to be purely a function of the size of the room, 
no account being taken of the heat losses. This method is 
manifestly inaccurate as the amount of air required depends of 
course upon the heat lost from the room. For rooms of average 
proportions and of ordinary construction, the volume method is 
usually successful, however, if carefully applied. The chart in 
Fig. 133 gives the size of leaders and risers required for rooms of 
various dimensions. It is permissible to reduce the size of the 
leader to which a riser is connected, as indicated by the chart, 
because of the acceleration of the circulation due to the stack 
effect of the riser. 







~ 




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i 14 

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8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24. 25 26 27 28 29 
Length of Room in Feet 
Based on Ceiling Height of 9 Feet 

Fig. 133. — Size of hot air pipes for rooms of various dimensions. 



182. Suggestions for Hot-air Piping. — The following rules 
should be observed in the installation of the leaders and risers. 

Never use smaller than 8-inch pipe for the leaders. 

When a leader is more than 15 feet long, add 1 inch to the 
diameter for each 4 feet or fraction thereof over 15 feet and 
increase the riser to correspond. 

Rooms on the sides of the house exposed to prevailing winds 
should have one size larger pipe than rooms of equal size on the 
other sides of the house. If the exposed rooms have a consider- 
able amount of glass surface, they should have pipes two sizes 
larger. 

Avoid horizontal pipes under the second floor if possible. 



202 



HEATING AND VENTILATION 



When unavoidable, make them one-fourth larger than the risers 
and give them all the pitch possible, avoiding square angles. 

In Table XL are given the equivalent areas of round pipes, 
rectangular pipes, and registers. 

Table XL. — Equivalent Sizes of Pipes and Registers^ 



Diameter 

of round 

pipe 


Area of pipe, 


Size flat riser 


Size side-wall 


Size round 


Size rect. 


square inches 


pipe 


register 


floor register 


floor register 


.8 


50 


3MX14 


8X12 


12 


8X12 


9 


64 


4X16 


10X12 


14 


10X12 


10 


78 


4X20 


12X12 


14 


10X16 


11 


95 


6X16 


12X15 


16 


12X15 


12 


113 


6X19 


14X15 


18 


12X20 


13 


132 


6X22 


14X18 


18 


14X18 


14 


154 


8X19 


16X18 


20 


14X22 


15 


176 


8X22 


16X20 


24 


16X20 


16 


201 


8X25 


18X20 


24 


16X24 


17 


227 


10X23 


18X24 


24 


18X24 


18 


254 


10X26 


20X24 


24 


18X27 


19 


283 


12X24 


20X26 


28 


20X26 


20 


314 


12X26 


22X26 


28 


20X30 


21 


346 


12X29 


24X27 


30 


22X30 


22 


380 


14X27 


24X30 


30 


24X30 


23 


415 


14X30 


27X27 


30 


24X32 


24 


452 


14X32 


28X28 


36 


24X36 



All measurements in inches. 

The circulation to a room which is unfavorably situated or 
which has a considerable amount of glass surface may be aided 
by installing a re-circulating duct from a register located beneath 
the windows to the lower part of the furnace casing. 

183. Foul-air Flues. — It is important that means be pro- 
vided for allowing the escape of air from the various rooms; 
for fresh warm air cannot enter unless it can displace an equal 
volume of room air. A fireplace is a very good form of foul-air 
flue and if the house is well provided with fireplaces, no other 
foul-air flues are necessary. Where several rooms open into each 
other and one of them has a fireplace, this may serve as a foul-air 
flue for all the rooms. 

The cracks around the windows and doors often serve to allow 
air to escape, but when located on the exposed side of the house, 
the pressure of the wind prevents the outflow of air and the air 

^ From "Handbook of National Warm Air Heating and Ventilating 
Association." 



HOT-AIR FURNACE HEATING 203 

supply to the room may be greatly retarded. For such rooms it 
is well to provide either a re-circulating duct or a foul-air flue. 

The foul-air flues should be enclosed in the inside partitions 
and the registers should be placed at the baseboard. The reason 
for such an arrangement is that the hot air entering the room 
opposite the window surfaces rises to the ceiling and passes along 
the ceiling to the windows where it is cooled, dropping to the floor 
and passing along it to the foul-air register. The hot-air register 
should be a sufficient distance from the foul-air register so that 
the hot air will not pass directly to the foul-air flue. 

A cheap foul-air flue can be made by having a register in the 
baseboard opening into the space between the studding, selecting 
a space that is open to the attic. A ventilator placed on the roof 
discharges the air from the attic. No two rooms should be con- 
nected to the same studding space. A still better arrangement 
is to extend each flue separately to the ventilator. 

The area of the foul-air flues should be at least 80 per cent, 
of that of the warm-air flues and they are often made equal in 
area to the latter. 

184. Forced Circulation. — Furnace systems are sometimes 
installed in which the circulation is produced by a fan. The 
principal advantage of such an arrangement is that the cir- 
culation is positive and is not affected by weather conditions. 
The fan, usually of the disc or propeller type, is placed in the 
cold-air inlet to the furnace and forces the air through the furnace 
and thence through the hot-air pipes to the rooms. Furnace 
systems with forced circulation are used principally where a 
considerable amount of air is required for ventilation and where 
an outfit is desired of lower first cost than an ordinary fan system. 

185. Pipeless Furnaces. — One type of furnace which de- 
serves but brief mention is the so-called '^pipeless" furnace 
system. In this system a single register is used, located im- 
mediately above the furnace, and consisting of two sections, 
one section supplying hot air and the other section being con- 
nected to a re-circulating duct leading back to the base of the 
furnace. It is evident that with such an arrangement the 
room above the furnace will receive the greatest amount of 
heat and that all the other rooms can receive heat only by the 
natural circulation of air through them. The advantage of the 
pipeless furnace is its low cost. It is strictly limited to very 
small houses or bungalows and is not successful if installed outside 



204 



HEATING AND VENTILATION 



of this field. It lacks one of the chief advantages of the ordinary 
hot-air system — the providing of fresh air for ventilation. 

186. Test of Hot-air Furnace. — The following is a summary 
of the results of a heat analysis of a hot-air furnace made at 
the University of Michigan.^ 



Test No. 



11 



2 Length of test — hours 

3 Number of firings 

5 Inlet temperature of air 

6 Average temperature of heated air 

7 Temp, of wet-bulb thermometer 

8 Temperature of dry-bulb thermometer 

9 Humidity, per cent 

12 Volume of air deUvered, cubic feet per minute 

14 Temperature of gases over fire, deg. F 

15 Temperature of gases in breeching, deg. F. . 

16 Draft in breeching, inches of water 

17 CO2 content of flue gases, per cent 



21 Kind of fuel 



22 Total weight of fuel fired 

23 Total weight of ash and refuse 

24 Proximate analysis of fuel, per cent. 

Moisture 

Volatile 

Fixed carbon 

Ash 

26 Heat value per pound as fired 

28 Total water evaporated from water pan, 

pounds 

Heat balance, per cent. 

43 Heat input in fuel 

44 Heat absorbed by air 

45 Heat given to water 

46 Heat given to air, gross 

47 Heat lost up the stack 

48 Heat lost in unburned fuel . . . . 

49 Heat lost from furnace by radiation 

50 Unaccounted for efficiency 



30.00 
2.00 

50.60 
113.70 

70.80 
112.00 

11.00 
,110.00 



51 Efficiency — net (Item 46) per cent 

52 Efficiency— gross (Items 46 + 49 + 3^ of 50) 
per cent 



309.00 
0.07 
10.26 
Mixed stove 

and egg 
anthracite 
255.00 
37.00 

0.78 

4.75 

88.61 

12.86 

12,856,00 

62.00 

100.00 
61.60 

2.05 
63.65 
11.65 

1.60 
11.00 
12.10 

63.65 

80.70 



31.00 

4.00 

39.60 

109.20 

64.70 

107.70 

7.00 

1,284.00 

691.00 

318.40 

0.076 

8.10 

Gas coke 

330.50 
16.50 

6.00 

3.60 

86.10 

4.30 

13,026.00 

123.00 

100.00 

63.00 

3.10 

66.10 

13.50 

0.70 

8.83 

10.87 

66.10 

80.36 



^"Heat Analysis of a Hot-air Furnace," by John R. Allen, Trans. 
A. S. H. & V. E.. 1916. 




HOT-AIR FURNACE HEATING 205 

It will be noted that the heat given up to the air passing 
through the furnace is from 63 to 66 per cent, of the heat input 
in the fuel. In most installations, however, the heat radiated 
from the furnace is largely utilized, making the ''gross" efficiency 
about 80 per cent. 

Problem 

1. Compute the required size of the hot-air pipes and of wall registers for 
the following rooms. 

Room No. Heat loss from room Floor 

1 16,000 First 

2 10,800 Second 

3 8,700 Third 

4 5,000 Second 



CHAPTER XV 
DESIGN OF FAN SYSTEMS 

187. Types of Fan Systems. — Fan systems are installed pri- 
marily to provide fresh air for ventilation, although in some 
classes of buildings they are preferable from a heating standpoint 
also. There are two general types of systems in use. In a simple 
ventilating system the heat lost through the walls of the building 
is supplied by direct radiation, and the air for ventilating is in- 
troduced at a temperature but slightly above that of the rooms. 
In the second type the heat losses are taken care of by the fan 
systern and no direct radiation is installed. This means that 
the air must be heated considerably above the room temperature, 
to a point dependent upon the heating requirements. 

The former system is usually the more suitable for buildings 
which require ventilation only part of the time, such as schools 
and office buildings. The proper temperature can be maintained 
in the building by means of the direct radiation and the fan 
system need be operated only when ventilation is required. 
Furthermore, the amount of air introduced can be limited to 
that actually required for ventilation. The fuel consumption 
is thus reduced to a minimum if the system is carefully operated. 
An objection to the combination system is the high first cost, 
which is considerably above that of a fan system alone. 

The second type, in which the heat losses from the building 
are supplied by the fan system, is most suitable for buildings 
which must be continuously ventilated. A system of this type 
must be operated whenever the building is to be heated and 
much more air may be introduced than is required for ventilation. 
In theatres and churches, which need only be heated when 
ventilation is required, this arrangement is suitable. In some 
cases means can be provided for re-circulating the air from the 
building when desired instead of drawing in fresh air. The 
fresh air need then be introduced only when ventilation is needed, 
the air being re-circulated when the building is unoccupied. 
Such fan systems, supplying both the heating and ventilating 

206 



DESIGN OF FAN SYSTEMS 



207 



requirements, are often used in industrial buildings and are 
termed ''hot-blast" systems. 

188. General Arrangement. — The usual arrangement of a 
simple fan system for heating is shown in Fig. 134. The air is 
drawn from the outside over a set of tempering coils which heat 
it up to about 70°. It is then drawn through a set of heating 
coils and discharged by the fan into the system of supply ducts. 
In the heating coils its temperature is raised from 70° to whatever 
temperature is demanded by the heating requirements. A 
bypass damper is provided beneath the heating coils by means 
of which tempered air may be admitted to the duct system and 




iTFTiT 

III I 

I I! II 
I I I II I 



m- 



K) 



Led 



Tempering 




Ean 
Keturn ^fain 



Fig. 134. — General arrangement of fan system. 

the temperature of the air in the ducts may be regulated to suit 
the heating requirements. 

Fan systems may be arranged either as ''draw-through" or 
"blow-through" systems. In the former the heating coils are 
located at the fan inlet and the fan discharges directly into the 
duct system. Such an arrangement is slightly the more efficient 
but the blow-through system is on the whole the more suitable 
for most classes of buildings as it permits of a better arrange- 
ment of the mixing dampers. 

189. Calculation of Air Quantities. — When ventilation only 
is considered the quantity of air to be handled by the fan is 
governed by the number of people in the building and the amount 
of air to be supplied per person. In Chapter XIII the con- 



208 HEATING AND VENTILATION 

siderations affecting ventilation requirements were discussed, 
and in Table XXXIX, page 181, are given the quantities required 
per person or the number of air changes per hour for various 
classes of buildings. 

If Q is the total quantity of air to be introduced per hour and 
Hv is the heat which must be added to the air in B.t.u. per hour, 
then: 

H. = QD,C^{t2 - h) (1) 

in which Cp = specific heat of air at constant pressure ( = 0.2415). 
ti = temperature of outside air. 
^2 = temperature of inside air. 
D2 = density of air at temperature ^2 in pounds per 
cubic foot. 

In this expression the heat absorbed by the water vapor is 
neglected but the formula is sufficiently accurate for ordinary 
purposes. If the minimum outside temperature, for which the 
system is to be designed, is 0° and the inside temperature is 70°, 
then I>2 = 0.07495 and formula (1) becomes 

Hy = QX 0.07495 X 0.2415(70 - 0) 

H, = 1.27Q (2) 

In the case of a fan system supplying the heat which is lost 
through the wall and glass surface, this amount of heat must be 
added to the air delivered. 

The air after entering the rooms is cooled to room temperature 
and discharged to the outside at that temperature. The total 
heat added to the air may therefore be thought of as being di- 
vided into two parts: (a) that which would be added were 
ventilation only being considered, which is the quantity required 
to raise the air from the outside temperature to room temperature, 
and (h) the additional amount added to supply the heat lost 
through the walls. The latter quantity may be expressed in 
the form 

H, = QD^C^iU - U) (3) 

in which t^ = temperature at which the air is delivered. 

D2 = density at room temperature, pounds per cubic foot. 

The air volume Q is ordinarily taken at room temperature, 
assumed to be 70°. 
Then 

H = H,-\- Hh = QD2Cj,{h - h) + QD^Cj^ih - U) (4) 



DESIGN OF FAN SYSTEMS 209 

The quantity of air Q may be governed either by the venti- 
lating requirements or by the heating requirements. If the heat 
loss from the building is large, a large quantity of air at the 
maximum temperature to which it is practicable to heat it, must 
be introduced, and this quantity may be greatly in excess of that 
required for ventilation. On the other hand, if the room is to 
contain a large number of people and if the heat loss is compara- 
tively small, then the quantity of air will be fixed by the venti- 
lation requirements and the temperature of delivery, ts, will be 
fixed by the heating requirements. 

Example. — Consider an auditorium which seats 400 people and which is 
to be ventilated with an allowance of 1500 cubic feet per hour per person. 
Assume that the fan system is to supply the heat losses as well as the ventila- 
tion requirements, and that a temperature of 68° is to be maintained. Let 
Hh, the heat loss through the exposed wall and glass surface be 860,000 
B.t.u. per hour, and assume that the air is to be delivered, under maximum 
conditions, at a temperature of 140°. From formula (3) Hh = QD^Cpit^ — ^2) 
and 

Hh ^ 860,000 

^ ~ D^Cj>{h - U) ~ 0.07524 X 0.2415(140-68) 

= 657,000 cubic feet per hour. 

Since the amount of air required for ventilation was set at 600,000 cubic 
feet per hour, it is evident that the amount introduced for heating require- 
ments will be ample for ventilation. 

Now, assume that instead of 400 people, there are 500 to be provided for, 
requiring 750,000 cubic feet per hour. The 657,000 cubic feet demanded by 
the heating requirements will then be insufficient and the quantity delivered 
must be that required for ventilation, its temperature, U, being below 140°. 
The temperature, ^3, may be computed from equation (3). 

860,000 = 750,000 X 0.07524 X 0.2415(^3 - 68) 
h = 131° 

190. Flow of Air in Ducts. — When air, like other fluids, is 
moved through a pipe or duct, a certain pressure or head is 
necessary to start and maintain the flow. This head has two 
components. The static head is that which is required to over- 
come the frictional resistance of the air against the surface of the 
duct. The velocity head is the pressure required to produce the 
velocity of flow. The sum of these two components is termed 
the total or dynamic head. 

The static and velocity heads are mutually convertible. The 
velocity head depends entirely upon the velocity of flow and if 
the velocity in the duct is decreased at any point because of an 
increase in the cross-sectional area, a portion of the velocity head 



210 HEATING AND VENTILATION 

will be converted into static head. Conversely, when the area 
is reduced, the static head is partially converted into velocity 
head. The interchange, however, is always accompanied by a 
certain amount of net loss of head, depending upon the abrupt- 
ness of the change in area and shape of the section in which the 
change of area takes place. 

The velocity head may be considered as the height of a column 
of air which will have at its base a pressure sufficient to produce 
the given velocity, the relation being represented by the common 
expression, v^= 2gh. To express the velocity head in inches 
of water, the usual standard, let 

D = density of air under the given conditions, pounds per 

cubic foot. 
Z>' = density of water = 62.3 pounds per cubic foot at 70°. 
hv = velocity head in inches of water. 
h = velocity head in feet of air. 
Then 

hD=^D' or h = Y2^ 
72 = 3600 X 2g X^^ 

in which V is the velocity in feet per minute. 

V = 1096.5 J| (1) 

191. Measurement of Flow. — The static head or pressure 
in an air duct may be thought of as the pressure tending to 
burst the duct and it may therefore be readily measured by 
means of a water gage communicating with the duct in the 
manner shown at A in Fig. 135. The deflection of the water 
levels will then indicate the static pressure directly in inches of 
water. The total or dynamic head is measured by a tube whose 
open end points against the flow as at B. Since the velocity 
varies at different points in the cross-section of the duct, any 
single reading of the total pressure applies only to the particular 
location of the tube in the duct. The velocity head, which is 
equal to the difference between the total and static heads, can 



DESIGN OF FAN SYSTEMS 



211 



be computed from them or can be measured directly by con- 
necting the U-tube as at C in Fig. 135. 

The relation between the velocity and the velocity head 
affords a convenient method for measuring the flow of air through 



ABC 

y.Jff Static IT Total I H 

I I Ereasure i -J*PresBure I | 



_i^Velocity 
Pressure 



. Fig. 135. 

pipes. For this purpose the pitot tube illustrated in Fig. 136 
is used in practice. The tube is inserted into the pipe in such 
a manner that the head A-B is parallel to the flow of air, with 
the end A toward the flow. The part A-B consists of an inner 



uct Conveying Air 



U' 



Static Press 



111 



icl [Press 



Air Cuttent 

■< 



\^ To Manometer 
^^ To Manometer 




Inclined Maaometer 




Fig. 136.— Pitot tube. 



tube which transmits the total pressure to the tube D and an 
outer jacket through which the static pressure is transmitted 
to the tube C. This outer jacket contains several small holes 
through which the static pressure is transmitted. The two 



212 



HEATING AND VENTILATION 



pressures are transmitted to the ends of the differential slant 
gage E, which is a U-tube arranged with one leg at an angle so 
that the linear deflection per inch of height is increased. Gages 
of this type are usually filled with oil but are calibrated to read 
in inches of water column. The reading on the gage is evidently 
the velocity head, being the difference between the static and 
total heads. 

As has been stated, the velocity of flow is not constant at all 
points in the cross-section of the duct. Near the walls it is 
retarded by the friction and it reaches a maximum at the center 
of the pipe. It is therefore necessary to measure the velocity at 
several points in the pipe in order to obtain an average figure. 
In a square or rectangular duct the cross-section is divided into 




1700 



1800 1900 2000 
Velocity 



Fig. 137. — Division of round pipe into annular zones. 



several equal rectangles and readings are taken with the pitot 
tube at the center of each of these divisions. The velocity cor- 
responding to the pressure at the point where each reading is 
taken is then computed from formula (1), Par. 190, in feet per 
minute. The average of these computed velocities is taken as 
the average velocity in the pipe. The quantity of air flowing 
can be readily computed from the velocity and the cross-sec- 
tional area of the pipe. 

For a round pipe the cross-sectional area should be divided 
into a number of annular zones of equal area and a traverse of the 
pipe should be made in both a vertical and a horizontal direction, 
as shown in Fig. 137. For each foot of pipe diameter the cross- 
section should be divided into at least three of these zones. 
Table XLI gives the distance from the center of the pipe at which 
each reading should be taken in per cent, of the pipe diameter. 
It is important that the velocities be computed separately and 
averaged, for the velocity varies as the square root of the pressure 



DESIGN OF FAN SYSTEMS 



213 



Table XLI. — Pipe Traverse for Pitot Tube Readings 

Distance from Center of Pipe to Point of Reading in Per Cent, of 

Pipe Diameter 



No. of 
equal areas 
in traverse 


No. of 
readings 


1st i?l 


2d R2 


3d 223 


4th Ri 


5th Rs 


6th iJe 


7th i27 


8th 728 


3 


12 


20.4 


35.3 


45.5 












4 


16 


17.7 


30.5 


39.4 


46.6 










5 


20 


15.5 


27.2 


35.3 


41.7 


47.4 








6 


24 


14.5 


25.0 


32.3 


38.2 


43.3 


47.9 






7 


28 


13.4 


23.1 


29.9 


35.3 40.1 


44.3 


48.2 




8 


32 


12.5 


21.6 


28.0 


33.2 37.6 


41.5 


45.1 


48.4 



and accurate results cannot be obtained by averaging the pressure 
readings. The method outhned above is the standard method 
adopted by the American Society of Heating and Ventilating 
Engineers.^ 




Fig. 138. — Anemometer. 



192. The Anemometer. — For very approximate results, the 
anemometer, Fig. 138, is a convenient instrument for measuring 
the flow of air at the duct outlets. For very low velocities it is 
not suitable, as the friction required to revolve the propeller is 

1 Report of Committee on Standardization of Use of Pitot Tube, Trans. 
A. S. H. & V. E., 1914. 



214 HEATING AND VENTILATION 

the source of a considerable error. In using the anemometer the 
face of the register is divided into a number of equal areas and 
the readings taken at the several areas are averaged. The dial 
is calibrated to read directly in feet and the velocity is obtained 
by taking the registration of the instrument during a definite 
period of time. 

193. Friction Loss. — The general expression for the friction of 
fluids in pipes (equation (3), page 132) is applicable to the flow 
of air: 

ci 2g 
or for round ducts of perimeter R and length L 

p_fRL W _fRL v^ 

a 2g o, 2g 

in which P = pressure required to overcome friction, pounds 
per square foot. 
a = cross-sectional area of duct, square feet. 
D = density of air, pounds per cubic foot. 
V = velocity, feet per second. 
/ = coefficient of friction. 
ha = height in feet of a column of air equivalent to P. 

It is more convenient to express the friction head in terms of 
inches of water. If the density of air at 70° be taken as 0.075 
and the density of water as 62.3 pounds per cubic foot then the 
head in inches of water is 

h = 0^^f^f = 0.00022 (^v^ 
62.3 Ci 2g a 

The value of / was found by Reitschel and other to be about 
0.0037 for smooth iron ducts. Prof. J. E. Emswiler^ reports 
values for/ ranging between 0.004 and 0.006 for velocities of 800 
feet per minute and over, the coefficient decreasing slightly as the 
velocity increases. For practical purposes a somewhat higher 
coefficient is used, giving larger duct sizes. Allowance is thereby 
made for roughness of the duct surfaces and for accidental 
obstructions. 

The chart in Fig. 139, which is pubUshed by the American 

1 See "Coefficient of Friction of Air Flowing in Round Galvanized Iron 
Ducts," by J. E. Emswiler, Trans. A. S. H. & V. E., 1916. 



DESIGN OF FAN SYSTEMS 



215 



Blower Co., gives the friction in inches of water per 100 feet 
length of duct for various quantities of air. The chart is for 
round ducts; to figure the friction in a square or rectangular duct, 
it is necessary first to obtain the diameter of the equivalent 
round duct, which can be done by means of Table XLII. 



o o o o o o 

to* -)J W" «J 00 o 




Friction in Inches Water Gage per 100 Feet '■ 
Fig. 139. — Frictional resistance in round air ducts. 



. Example. — Find the friction loss in a 20 by 10-inch duct 67 feet long, 
carrying 2000 cubic feet of air per minute. From Table XLII we find that 
the diameter of the equivalent round duct is 15.4 inches. From the chart 
in Fig. 139 the friction drop per 100 feet of duct for the given flow and for 
a diameter of 15.4 inches is readily found to be 0.31 inches of water. For 
a length of 67 feet the drop would be 0.3 X 0.67 = 0.201 inches of water. 



216 



HEATING AND VENTILATION 



Table XLII. — Diameter of Round Ducts Equivalent to Rectangular 
Ducts of Various Dimensions 



Side 


4 


6 


8 


10 


12 


14 


15 


16 


18 


20 


22 


24 


rectangular 
















































duct 










Equivalent diameters 








3 

4 


4.4 
























5 


4.9 
























6 


5.4 


6.6 






















7 


5.8 


7.0 






















8 


6.1 


7.6 


8.8 




















9 


6.5 


8.0 


9.3 




















10 


6.8 


8.4 


9.8 


11.0 


















11 


7.1 


8.8 


10.2 


11.5 


















12 


7.4 


9.2 


10.7 


12.0 


13.2 
















13 


7.6 


9.6 


11.1 


12.5 


13.7 
















14 


7.6 


9.9 


11.5 


12.9 


14.3 


15.4 














15 


8.2 


10.2 


11.9 


13.4 


14.7 


16.0 


16.5 












16 


8.4 


10.5 


12.3 


13.8 


15.2 


16.5 


17.1 


17.6 










17 


8.6 


10.8 


12.6 


14.2 


15.7 


17.0 


17.6 


18.2 










18 


8.9 


11.1 


13.0 


14.6 


16.1 


17.4 


18.1 


18.7 


19.8 








19 


9.1 


11.4 


13.3 


15.0 


16.5 


17.9 


18.6 


19.2 


20.4 








20 


9.3 


11.6 


13.6 


15.4 


17.0 


18.4 


19.0 


19.7 


20.9 


22.0 






22 


9.7 


12.1 


14.2 


16.1 


17.8 


19.2 


19.9 


20.6 


21.9 


23.1 


24.2 




24 


10.0 


12.6 


14.8 


16.8 


18.5 


20.0 


20.8 


21.5 


22.8 


24.0 


25.2 


26.4 


26 


10.4 


13.1 


15.4 


17.3 


19.2 


20.8 


21.6 


22.3 


23.8 


25.1 


26.3 


27.5 


28 


10.8 


13.5 


15.9 


18.0 


19.8 


21.5 


22.4 


23.1 


24.6 


26.0 


27.3 


28.5 


30 


11.0 


13.9 


16.4 


18.5 


20.5 


22.2 


23.1 


23.9 


25.4 


26.8 


28.2 


29.5 


32 


11.3 


14.3 


16.9 


19.1 


21.1 


22.9 


23.8 


24.6 


26.2 


27.7 


29.1 


30.5 


34 


11.6 


14.7 


17.3 


19.6 


21.6 


23.5 


24.4 


26.3 


26.9 


28.5 


30.0 


31.3 


36 


11.9 


15.1 


17.7 


20.1 


22.2 


24.2 


25.1 


26.0 


27.7 


29.3 


30.8 


32.2 


38 


12.2 


15.4 


18.2 


20.6 


22.8 


24.8 


25.8 


26.7 


28.4 


30.0 


31.5 


33.1 


40 


12.5 


15.7 


18.6 


21.1 


23.3 


25.4 


26.4 


27.3 


29.1 


30.8 


32.4 


33.9 


42 


12.7 


16.1 


19.0 


21.6 


23.8 


25.9 


26.9 


27.9 


29.8 


31.4 


33.0 


34.5 


44 


13.0 


16.4 


19.4 


22.0 


24.3 


26.5 


27.5 


28.5 


30.3 


32.1 


33.7 


35.3 


46 


13.3 


16.7 


19.8 


22.4 


24.8 


27.0 


28.1 


29.1 


31.0 


32.8 


34.6 


36.2 


48 


13.5 


17.0 


20.1 


22.8 


25.2 


27.5 


28.6 


29.6 


31.6 


33.4 


35.2 


37.0 


50 


13.7 


17.3 


20.4 


23.2 


25.7 


28.0 


29.2 


30.3 


32.2 


34.1 


35.9 


37.6 


52 


13.9 


17.6 


20.8 


23.6 


26.2 


28.5 


29.6 


30.7 


32.9 


34.7 


36.5 


38.3 


54 


14.1 


17.9 


21.1 


24.0 


26.6 


29.0 


30.1 


31.2 


33.4 


35.3 


37.2 


38.9 


56 


14.3 


18.2 


21.5 


24.4 


27.0 


29.5 


30.6 


31.7 


33.9 


35.9 


37.8 


39.6 


58 


14.6 


18.4 


21.8 


24.7 


27.4 


30.0 


31.1 


32.2 


34.4 


36.4 


38.4 


40.3 


60 


14.7 


18.7 


22.1 


25.1 


27.8 


30.5 


31.6 


32.7 


34.9 


37.1 


39.1 


40.9 


62 


15.0 


19.0 


22.4 


25.5 


28.2 


30.9 


32.1 


33.2 


35.4 


37.7 


39.6 


41.6 


64 


15.1 


19.2 


22.7 


25.9 


28.6 


31.3 


32.6 


33.7 


35.9 


38.2 


40.2 


42.2 


66 


15.3 


19.5 


23.0 


26.2 


29.0 


31.7 


33.0 


34.2 


36.4 


38.7 


40.8 


42.8 


68 


15.5 


19.7 


23.3 


26.5 


29.4 


32.1 


33.4 


34.7 


36.9 


39.2 


41.4 


43.4 



194. Pressure Loss Due to Obstructions. — The loss of pressure 
caused by various obstructions, such as elbows, branches, etc., 
is usually expressed as a multiple of the velocity head. The 
actual loss, however, is of course a loss of static head, since the 
velocity head at all points in a pipe, for a given quantity of 



DESIGN OF FAN SYSTEMS 



217 



air flowing, depends entirely upon the cross-sectional area at 
each point. 

The center line radius of elbows should be equal to at least 
1}^ times the width of the duct, as demonstrated by Frank L. 
Busey,^ who obtained the following results for elbows of square 
cross-section : 



Center line radius 
cent, of pipe wi 


in 
dth 


per 


Per 


cent, of velocity 
head lost 


50 








95 


75 








34 


100 








17 


150 








8 


200 








7 



Another method is to add to the actual length of straight pipe 
a certain length which will have the same friction loss as that due 
to the resistance in question. The following table gives the loss 
of pressure due to various obstructions. 

Table XLIII. — Pressure Loss Due to Various Obstructions 



Per cent, of 
velocity 
pressure 



Equivalent 

length of 

straight pipe 



Round elbow (c. 1. radius 1}4 X width) 

Sharp elbow 

Square tee 

Branch from main duct 
Angle, 15 degrees (per cent, of v. p. in branch).. 

30 degrees 

45 degrees 

Abrupt entrance to pipe 

Coned entrance to pipe 

Registers (free area = duct area = }4 total area 

of register). 



8-10 
100.0 
100.0 

10 
20 
25 
50-90 
25 
1.25 



10 X width 



Air washers: 


Velocity through washer, 
feet per minute 


Pressure loss, 
inches of water 




400 




0.15 




500 




0.25 




600 




0.35 




700 




0.45 



Example. — Given an air duct of square cross-section carrying air at a 
velocity of 900 feet per minute, and at a temperature of 70°. Find the loss 

^See "Loss of Pressure Due to Elbows in the Transmission of Air 
through Pipes or Ducts," by Frank L. Busey, Trans. A. S. H. & V. E., 1913. 



218 HEATING AND VENTILATION 

of head due to an elbow of diameter 1^ X width. From formula (2), page 

(900 \ 2 
1096 5/ ^ 0-07495 = 0.0505 inches. The 

pressure loss is 0.08 X 0.0505 = 0.004 inches. 

195. Proportioning Duct Systems. — It is highly desirable that 
the size of the ducts be intelligently selected and that the pres- 
sure loss in the system be computed as accurately as possible. 
The principal reason for doing this is to insure the selection of a 
fan of the proper characteristics; for in order that the required 
quantity of air be delivered it is necessary that a fan be selected 
with working head sufficient to overcome the resistance of the 
system. Furthermore, the proper proportioning of the various 
branches will result in the delivery of the proper air quantities 
to the various rooms without too great a dependence upon the 
use of the dampers. 

In designing a duct system it is necessary first to select the 
static resistance against which the fan is to operate. Since the 
power consumption depends upon the resistance, the cost of 
power is a consideration in air-duct design. A reduction in the 
power required can be obtained by increasing the duct sizes; 
but the increased cost of the larger ducts and the greater space 
required are the opposing factors. 

There are two general systems of air distribution and the 
method of choosing the duct sizes depends upon the type of 
system. In public buildings, particularly in schools, the single- 
duct system is used, in which the air is delivered to a plenum 
chamber by the fan and separate ducts radiate to the various 
rooms. In such a system the duct having the greatest resistance 
is first designed, which fixes the pressure to be carried in the 
plenum chamber. The other ducts are then so designed as to 
deliver the required quantities with the given pressure differential. 
The longest duct is designed on a basis of certain assumed 
velocities; Table XLIV gives those recommended by W. H. 
Carrier: 

Table XLIV. — Velocities in Single-duct Systems 

Velocity, feet per minute 

Vertical flues 400-750 

Horizontal runs 700-1200 

Wall registers! 200-400 

Floor registers^ 125-175 

1 Over gross area. 



DESIGN OF FAN SYSTEMS 



219 



In industrial buildings the trunk duct system is used, consist- 
ing of one or more main ducts with branches taken off at inter- 
vals. Such ducts are so proportioned as to give an equal friction 
loss per foot of length. The outlets are designed for certain 
velocities depending upon the size of the room and upon the 
distance through which it is desired to blow the air, the possi- 
bility of objectionable drafts being considered. It is customary 
to assume an outlet velocity of from 700 to 1500 feet per minute, 
an average figure being 1000 feet per minute. The branches from 
the main duct should be so proportioned as to deliver the re- 
quired air quantities and it is usually best to provide dampers 
on the outlets so that any inequalities in distribution can be ad- 
justed after the system is installed. It is desirable to design 
all air ducts on a basis of an air density corresponding to the 
maximum air temperature to be expected. 



1 S 



^ 



31 n I 



P 




.J 



" jJ~^ 1600 C.F.M. 

i 

I 



250'- 



-^ 



Fig. 140. 

196. Example of Single Duct System. — Assume that a single 
duct system is to be designed and that the longest duct is ar- 
ranged as in Fig. 140, the air temperature being 70°. 

We will figure the horizontal run on a basis of 1000 feet per 
minute and a duct of rectangular section will be used. The area 
of the horizontal duct will be 1600 -^ 1000 = 1.6 square feet and 
a 12- by 19-inch duct will be used. For the riser a velocity of 
600 feet per minute will be used and the required area is 1600 -^ 
600 = 2.75 square feet, requiring a 16- by 24-inch duct. From 
Table XLII we find that the diameter of a round pipe equivalent 
to a 12- by 19-inch rectangular duct is 16.5 inches and for a 16- by 
24-inch duct 21.5 inches. From the chart in Fig. 139 we find 



220 HEATING AND VENTILATION 

that a pipe of 16.5 inches diameter will transmit 1600 c.f.m. 
with a friction loss of 0.14 inches per 100 feet, and the loss for a 
21.5-inch pipe is 0.034 inches per 100 feet. To the actual length 
of straight pipe we must add the equivalent of the elbows, which 
may be taken (see Table XLIII) as ten times the actual width of 
the duct measured on the radius of the elbow. The total friction 
drop due to the straight pipe is then as follows : 

(250 + 10) X ^ + (40 + 13.3) X ^^ = 0.382 inch 

The resistance of the register may be taken as 1.25 times the 
velocity head corresponding to a register velocity of 300 feet 
per minute, upon which basis the size of the register will be 
selected. The velocity head we may compute by means of 
formula (2), page 210, 

K = (1^5) ' X 0.07495 = 0.0056 inch 

The loss through the register is 0.0056 X 1.25 = 0.007 inch. 
The loss at the entrance to the duct from the plenum chamber we 
will take as 80 per cent, of the velocity head corresponding to the 
velocity of 1000 feet per minute. 

0.80 XK = 0.80 X (t^S^) ' X 0.07495 = 0.050 inch. 
\1096.5/ 

The total resistance of the duct is then 

0.382 + 0.007 + 0.050 = 0.439 inch 

and the total pressure in the plenum chamber must be equal to 
this plus the velocity head corresponding to 1000 feet per minute 
or 0.439 + 0.062 = 0.501 inch. The remaining ducts must 
then be of such a size as to use up this available total pressure of 
0.501 inch. 

Assume the following data for one of the ducts: 

Quantity of air delivered, 1150 c.f.m. 

Register velocity, 300 feet per minute. 

Velocity, throughout entire length, 800 feet per minute. 
Total equivalent length, including 

resistance of elbows, 110 feet. 

The following quantities can be computed : 

Resistance of register = (j^^) ' X 0.07495 = 0.0056 inch. 



DESIGN OF FAN SYSTEMS 221 

/ 800 \ 2 
Loss at entrance to duct = 0.80 X ThoaT X 0-07495 = 

\1096.5/ „ „„^ . , 

0.032 inch. 

(800 \ 2 
jQ^Q^j X 0.07495 = 0.040 inch. 

Static head to be used up by friction = 0.501 — (0.0056 + 
0.032 + 0.040) = 0.423 inch. 

The friction loss per 100 feet of duct must then be 0.423 -^ 1.10 
= 0.385 inch. From the chart in Fig. 139 the diameter of the 
round pipe which will give this friction loss for 1150 c.f.m. is 
12.0 inches. This is equivalent (see Table XLII) to a rectangular 
pipe 10 by 12 inches or 8 by 15 inches, either of which could be 
used. The equivalent length allowed for the elbows, which 
must necessarily have been estimated, should be revised if the 
computed width of the duct is greatly different from the assumed 
width upon which the equivalent lengths were estimated, and 
the calculation repeated. 

197. Correction for Temperature. — The quantities for which 
the duct sizes are computed are the volumes at the actual 
temperature of the air flowing. On the other hand, the 
volumes fixed by the heating and ventilating requirements are 
on a basis of room temperature, i.e., about 70°. The volumes 
upon which the air ducts are designed must therefore be de- 
termined by multiplying the volumes at 70° by the ratio:. 

Density of air at 70° 
Density of air at duct temperature 

These ratios are given in Table XXXVI, page 176, in the column 
headed ''Ratio to Volume at 70°F." 

198. Trunk-line System. — In a trunk-line system, the pro- 
cedure would be as follows: 

Assume a system laid out as in Fig. 141, in which the quan- 
tities as given are on a basis of 70°. The system will be de- 
signed for a temperature of 135° and the actual quantities flowing 
in the various sections are as follows; 

A-B 11,100 X 1.1230 = 12,465 

B-C 5,800 X 1.1230 = 6,513 

C-D 1,800 X 1.1230 = 2,021 

B-E 3,300 X 1.1230 = 3,706 

E-F 1,500 X 1.1230 = 1,684 

The total head at point A must be equal to the friction loss 
in the trunk duct plus the velocity head at D, the end of 



222 



HEATING AND VENTILATION 



the trunk duct. The method of proportioning by a uniform 
friction loss leads to a reduction in the velocity toward the 
end of the trunk and a consequent conversion of some of the 
velocity head to static head. The absolute values of the veloc- 
ity and static heads at A are not important,, the require- 
ment being that their sum be equal to the friction loss plus 
the velocity head at D. On a basis of velocity of 1000 feet per 

minute the velocity head at D will be equal to L^q^ , ) X 0.06675 

= 0.055 inch on a basis of 135°. The friction drop may be fixed 
arbitrarily and we will choose it in this case as 0.20 inch per 
100 feet, giving a total pressure at point A of 0.20 X 2.25 + 
0.055 = 0.505 inch. For a friction drop of 0.20 inch per 100 



h 



75- 






11.100 




Fig. 141. 

feet the diameters of sections A-B, B-C, and C-D, would be 
respectively 34.0, 26.0, and 17 inches. The diameter of the 
outlet at D would be increased to 19 inches to give the re- 
quired outlet velocity of 1000 feet per minute. The branch 
pipe could be designed for the same pressure loss per unit 
length but it is more economical to take advantage of the full 
available head and reduce the size of the pipe. The static head 
at B can be found by subtracting from the static head at A the 
loss in section A-B. Allowing for the loss due to entrance in the 
branch at B and for the final velocity head at F the allowable 
friction loss in sections BE and EF can be determined and the 
size of pipe chosen accordingly. All outlets should be provided 
with dampers so that the proper delivery can be obtained by 
adjusting them after the system is installed. 




DESIGN OF FAN SYSTEMS 



223 



199. Power Required for Moving Air. — The power required 
for moving air through a system of ducts may be expressed as 
follows : 

Let p = unit total pressure, inches of water. 

a = cross-sectional area of duct, square feet. 
V = velocity of air, feet per minute. 

Then the horsepower required is 
pav X 144 



Hp, = 



12 X 2.31 X 33,000 



= 0.000158 pav 



(1) 



If q is the volume of air delivered per minute in cubic feet, then 
q = av and 

Hp. = 0.000158 pq 

200. Theory of the Centrifugal Fan.— The centrifugal fan 
consists fundamentally of a wheel having several radial vanes 
revolving in a casing. Air enters near 
the axis of the wheel, flows to the cir- 
cumference under the influence of the 
centrifugal force produced by the rota- 
tion, and is discharged through the out- 
let which is located tangentially with 
respect to the fan wheel. The pressure 
created in a fan has two separate and 
independent sources, (a) that due to 
the centrifugal force imparted to the 
masses of air enclosed between the vanes, 
and (b) the pressure due to the linear velocity of the air as it 
leaves the tip of the blades. The efficient conversion of the 
velocity head into static head depends upon the proper design of 
the fan housing, as will be shown later. 

Fig. 142 represents an elementary centrifugal fan. Consider 
a thin layer of air of thickness dx between two of the vanes at a 
distance x from the axis and having an area of >S. The volume 
of this layer of air is then Sdx, and if its density is D, then the 
weight will be SdxD. Assume that the fan outlet is completely 
closed and that the wheel revolves at the rate of co radians per 
second. Then the centrifugal force 

co^xSdxD' 
df = - 




Fig. 142. 



^ Centrifugal force = 



for a mass m at radius 



224 



HEATING AND VENTILATION 



df 



The unit pressure dp corresponding to df is evidently = ^ and 



the equivalent head 



Then 



"^^ D SD 



dh = 



)'^xdx 



Let ri be the radius at the base of the blade and r2 the radius at 
the tip. Then 



=r 



^'xdx 



2g 



If the entire column of air between the two blades from the axis 
to the radius r2 be assumed to be affected, then ri = and 



h = 



2g 



If V is the linear tip speed then v = cor2 and 



h = 



The second source of pressure is that equivalent to the velocity v 
of the air at the blade tips which is equal to 

7)2 



h' = 



2g 



The total pressure or head developed under the assumed condi- 
tions would then be 

h + h' = - 



The above analysis is approximate only and is complicated 
under actual conditions by the effect of the various sources of 
pressure loss and by the fact that the conversion of the velocity 
head into static head is only partial. The analysis serves to 
show, however, the relation between the pressure developed by a 
centrifugal fan and the fan speed. ^ 

201. Fan Blades and Housings. — Fan blades may be designed 
in either of three ways: radial, curved, forward {i.e., in the 
direction of rotation) or curved backward. In Fig. 143 is shown 

^ For a complete discussion of the subject see ''Heating and Ventilating of 
Buildings," by R. C. Carpenter. 



DESIGN OF FAN SYSTEMS 



225 



graphically the effect in the resultant velocity of the air due to 
the different blade designs. The air leaving the tip of the blade 
has a velocity component Vi, parallel to the blade and a tangential 
component V2. If the blade is curved forward the resultant 
velocity v will be greater than that in the straight-blade type 
and if curved backward the resultant velocity will be decreased. 
The velocity head developed by the fan wheel is considerably 
greater than is required, while the static head, which is the force 
necessary to move the air against the frictional resistance of 
the duct system is low. The velocity head is therefore partially 
converted into static head by designing the housing in a suitable 
scroll shape so that the velocity of the air is gradually reduced. 
The efficiency with which the conversion to static head takes 
place depends upon the proper design of the housing. It is the 




Straight Forward Backward 

Fig. 1^3. — Effect of various blade designs. 

static head developed by a fan which is useful in overcoming 
duct resistance and before the velocity head can become available 
it must be converted into static head. Generally speaking, the 
fan which has the greater static head in proportion to velocity 
head is the more desirable; although the velocity head may be 
further converted to static head after it leaves the fan if the 
velocity is reduced by a gradual enlargement of the duct area. 

202. Power Required by a Fan. — It has been shown that the 
power required for moving air is 

^ 12 X2.31 X 33,000 

in which the pressure p is expressed in inches of water. 

If the pressure is expressed in terms of the equivalent column of 

air of height h, then 

^ 33,000 
in which D is the density of the air in pounds per cubic foot. 

15 



226 HEATING AND VENTILATION 

In a fan the actual head developed is only a portion of the 

theoretical head — and is represented approximately by 

The power required to drive a fan is then 

^^' g ^33,000 

in which c is a factor which takes into account the mechanical 
losses in the fan. Combining all of the constant factors we have 

Hp. = Kv'^QD 

V being the peripheral velocity, which varies directly as the speed 
of the fan. Since Q varies directly as the speed, the power re- 
quired varies as the cube of the speed. 

203. Fan Performance. — From a consideration of the fore- 
going, the following laws can be stated as to the performance 
of centrifugal fans: 

For a .given fan delivering air through a given piping system — 

1. The capacity varies directly as the fan speed. 

2. The pressure varies as the square of the speed, 

3. The speed and capacity vary as the square root of the pressure. 

4. Horsepower varies as the cube of the speed or capacity. 

5. Horsepower varies as the (pressure) .^^ 
For a constant pressure — 

6. The speed, horsepower and capacity vary as the square root 

of the absolute temperature of the air. 
At constant capacity and speed — 

7. The horsepower and pressure vary inversely as the absolute 

temperature of the air. 

204. Fan Efficiency. — The true efficiency of a fan may be 
defined as the ratio of the work done in moving the air to the 
energy input to the fan. The total efficiency which is the true 
efficiency is computed from the total pressure, while the so-called 
static efficiency is computed from the static pressure. The 
efficiency may then be expressed as follows: 

c^ ^. rr, ' 0.000157 X c.f.m. X static pressure in inches 
btatic efficiency = r 

rry J. ^ rn ' 0.000157 X C.f.m. X total pressure in inches 
1 otal efficiency = r — 

in which hp. represents the horsepower input to the fan, and the 



II 



DESIGN OF FAN SYSTEMS 



227 



factor 0.000157 is the power required to move 1 cubic foot of 
air per minute against a pressure of 1 inch of water. 

205. Straight-blade and Multi-blade Fans. — Centrifugal fans 
are of two general types. The older type, the "steel-plate" fan, 
has a relatively small number of radial blades which are nearly 
plane surfaces. The more recently developed ' ' multi-blade ' ' type 
has a large number of short, curved blades on a wheel of com- 
paratively small diameter. In the multi-blade type the blades 
are usually curved forward as in Fig. 143, so that the pressure 



M 220 
a 

1 200 

o 

2 180 

M 
O 

O 



,160 



3 2 
1^140 

o gl20 

S. 2-100 



20 

































































^ 
















^ 


^ 


^^ 


Pressure Characteristic of 
Forward Curved Blade Fans 










^ 


^^ 


























■^ 


^^ 




































































- 




-^ 
























T 


ressu 
Strai 


e Ch 

ght B 


iracte 
lade 


ristie 
Fans 


Of 






^ 






































































■^ 







































































20 



60 80 100 

Per Cent of Rated Capacity 



120 



140 



100 



Fig. 144. 



-Pressure characteristics of straight-blade and multi-blade fans at 
constant speed. ^ 



developed will be greater than that corresponding to the pe- 
ripheral velocity. 

The two types of fans have inherently different characteristics. 
In a straight-blade fan operated at constant speed the total pres- 
sure developed decreases as the output of the fan is allowed to in- 
crease by reason of a lessened resistance. The multi-blade fan 
develops an increasing total pressure as its output is increased 
under the same conditions. In Fig. 144 are shown the pressure 
characteristics of the two types. The vertical ordinate is in 
terms of the ratio of the total pressure to the pressure corre- 

1 From "The Centrifugal Fan," by Frank L. Busey, Trans. A. S. H. & 
V. E., 1915. 



228 



HEATING AND VENTILATION 



spending to the peripheral velocity, this standard being used 
simply to make the curves comparable. The practical signifi- 
cance of these differing characteristics is evident when the action 
of a fan supplying a system of ducts is considered. With a 
straight-blade fan if one part of the duct system were shut off 
and the fan speed is unchanged the result would be an increase 
in the amount of air delivered to the other rooms. With a multi- 
blade fan, on the other hand, the quantity dehvered through 
the remaining ducts would not be greatly altered. Other advan- 
tages of fans of the multi-blade type are the smaller space occupied 
and the fact that their higher speed makes it possible to connect 
them direct to motors. The higher speed also reduces the cost 
of the motor in some cases. In general the multi-blade type 
is the more suitable for ventilating systems. 




Fig. 145. — Wheel of straight-blade fan. Wheel of multi-blade fan. 



206. Commercial Types. — In Fig. 145 are shown the wheels 
of a straight-blade and of a multi-blade fan and in Fig. 146 is 
shown the casing of a multi-blade fan. The general appearance 
of the casings of the two types is quite similar, the multi-blade 
fan being somewhat smaller in diameter and of greater width for 
the same capacity. Fans can be obtained with the discharge 
opening at various angles and with the inlet opening on either 
side. In some cases fans of double width, having an inlet on 
both sides, are used. 

207. Selection of a Fan. — Before selecting a fan for a given 
installation it is necessary to know the quantity of air to be 
handled and the static resistance of the duct system. The total 
pressure against which the fan must operate is the sum of the 



DESIGN OF FAN SYSTEM'S 



229 



static resistances on both the suction and the discharge sides 
of the fan plus the velocity head at the fan outlet, which can be 
determined from the volume of air delivered and the size of the 
outlet. The size of fan which will fill the requirements is 
best obtained from the data published by the various fan manu- 
facturers. It is usually possible to obtain the same capacity 
and static head from two or more different size fans. Frequently 
the fan which operates the most efficiently under the given con- 
ditions is not the lowest in first cost and the selection must be 
governed by the relative importance of these factors. 




Fig. 146. — Casing of multi-blade fan. 

208. Fan Tables. — The exact performance to be expected of a 
fan under any given conditions can be obtained from the tables 
published by the manufacturers. There are two kinds of fan 
tables — the ''total pressure" tables, which give the speed, ca- 
pacity, and horsepower for the various size fans at the most 
efficient point for various total pressures; and the more complete 
"static pressure" tables, which give the performance at points 
on either side of the most efficient point. Tables XLV and 
XL VI are, respectively, the total pressure table for various sizes 
of one type of multi-blade fan, and the static pressure table for a 
multi-blade fan of one particular size, the latter being in a some- 



230 



HEATING AND VENTILATION 



what condensed form. More complete static pressure tables for 
both steel plate and multi-blade fans may be found in the Ap- 

Table XLV. — Capacities of Buffalo Niagara Conoidal Fans (Type N) 

Under Average Working Conditions — at 70°F. 

AND 29.92 Inches Barom.* 



Fan No. 


Mean 
diam. of 
blast wheel 


Area of 

outlet, 

square feet 


^^-in. total press, 
or 0.217 oz. 


H-in. total press, 
or 0.288 oz. 




R.p.m. 


Vol. 


Hp. 


R.p.m. 


Vol. 


Hp. 


3 


155/^ 


1.31 


413 


1,490 


0.13 


478 


1,720 


0.19 


3H 


181^ 


1.79 


354 


2,030 


0.17 


409 


2,350 


0.26 


4 


201.^ 


2.33 


310 


2,650 


0.22 


358 


3,070 


0.34 


4J^ 


23H 


2.95 


276 


3,360 


0.28 


318 


3,880 


0.43 


5 


26i.i 


3.64 


248 


4,150 


0.35 


287 


4,790 


0.53 


5y2 


283,i 


4.41 


225 


5,020 


0.42 


260 


5,800 


0.65 


6 


3134 


5.25 


207 


5,970 


0.50 


239 


6,900 


0.77 


7 


36h 


7.14 


177 


8,130 


0.68 


205 


9,400 


1.05 


8 


42 


9.33 


155 


10,610 


0.89 


179 


12,260 


1.37 


9 


47 


11.81 


138 


13,450 


1.12 


159 


15,520 


1.73 


10 


52 


14.58 


124 


16,580 


1.39 


143 


19,160 


2.14 


11 


58 


17.64 


113 


20,070 


1.68 


130 


23,180 


2.58 


12 


63 


21.00 


104 


23,880 


2.00 


119 


27,590 


3.08 


13 


68 


24.65 


95 


28,040 


2.35 


110 


32,370 


3.61 


14 


73 


28.68 


89 


32,520 


2.72 


102 


37,550 


4.19 


15 


78 


32.80 


83 


37,330 


3.13 


96 


43,100 


4.80 



Static pressure is 77}'^ per cent, of total press. 

Table XLV. — {Coniinued) 



Fan No. 


Mean 

diam. of 

blast wheel 


Area of 

outlet, 

square feet 


^^-in. total press, 
or 0.360 oz. 


Ji-in. total press, 
or 0.433 oz. 




R.p.m. 


Vol. 


Hp. 


R.p.m. 


Vol. 


Hp. 


3 


155^ 


1.31 


533 


1,930 


0.27 


585 


2,110 


0.35 


W2 


18H 


1.79 


457 


2,620 


0.37 


501 


2,870 


0.48 


4 


20^^ 


2.33 


400 


3,430 


0.48 


439 


3,750 


0.63 


m 


23H 


2.95 


356 


4,340 


0.60 


390 


4,750 


0.80 


5 


26^^ 


3.64 


320 


5,350 


0.74 


351 


5,870 


0.98 


5H 


283/i 


4.41 


291 


6,470 


0.90 


319 


7,100 


1.19 


6 


313/i 


5.25 


267 


7,710 


1.07 


292 


8,450 


1.41 


7 


36H 


7.14 


229 


10,490 


1.46 


251 


11.500 


1.92 


8 


42 


9.33 


200 


13,700 


1.91 


219 


15,020 


2.51 


9 


47 


11.81 


178 


17,340 


2.41 


195 


19,000 


3.18 


10 


52 


14.58 


160 


21,400 


2.98 


175 


23,460 


3.93 


11 


58 


17.64 


146 


25,900 


3.60 


160 


28,390 


4.75 


12 


63 


21.00 


133 


30,820 


4.29 


146 


33,780 


5.65 


13 


68 


24.65 


123 


36,180 


5.03 


135 


39,650 


6.63 


14 


73 


28.68 


114 


41,950 


5.84 


125 


45.990 


7.69 


15 


78 


32.80 


107 


48,160 


6.70 


117 


52,790 


8.83 



Static pressure is 77H per cent, of total press. 

1 From "Fan Engineering," Buffalo Forge Co. 




DESIGN OF FAN SYSTEMS 



231 



pendix, pages 276 to 299. The static pressure tables are the 
better adapted for general use. The total pressure can be found 
for any conditions by adding to the static pressure the velocity 
pressure as given in the third column in Table XL VI. 

Table XLVI.— No. 10 Niagara Conoidal Fan (Type N) 
Capacities and Static Pressures at 70°F. and 29.92 Inches Barom.^ 



Outlet 
velocity, 


Capac- 
ity, cu. 
ft., air 


Add 
for 


H-in. s.p. 


H-in. s.p. 


1-in. s.p. 


1^^-in. s.p. 


2-in. s.p. 


total 






















ft.-min. 


per 
min. 


press. 


R.p.m. 


Hp. 


R.p.m. 


Hp. 


R.p.m. 


Hp. 


R.p.m. 


Hp. 


R.p.m. 


Hp. 


1,400 


20,410 


0.122 


164 


2.92 


206 


4.61 


243 


6.59 


308 


11.1 






1,500 


21,870 


0.141 


163 


3.13 


204 


4.78 


240 


6.83 


305 


11.5 






1,600 


23,330 


0.160 


164 


3.42 


202 


5.02 


238 


7.05 


302 


11.8 


357 


17.0 


1,700 


24,790 


0.180 


165 


3.74 


201 


6.30 


235 


7.28 


299 


12.1 


353 


17.5 


1,800 


26,240 


0.202 


166 


4.13 


200 


6.61 


233 


7.59 


295 


12.4 


350 


17.9 


1,900 


27,700 


0.225 


168 


4.55 


200 


6.01 


232 


7.91 


293 


12.7 


347 


18.3 


2,000 


29,160 


0.250 


171 


5.04 


200 


6.48 


231 


8.32 


291 


13.0 


343 


18.7 


2,100 


30,620 


0.275 


174 


5.56 


201 


7.00 


231 


8.77 


288 


13.5 


340 


19.2 


2,200 


32,080 


0.302 


177 


6.12 


203 


7.54 


230 


9.31 


286 


13.9 


338 


19.6 


2,300 


33,540 


0.330 


180 


6.76 


205 


8.16 


231 


9.92 


285 


14.4 


336 


20.1 


2.400 


34,990 


0.360 


183 


7.43 


207 


8.86 


232 


10.60 


284 


16.0 


332 


20.6 


2,600 


37,910 


0.422 


190 


8.95 


213 


10.40 


235 


12.10 


282 


16.3 


329 


21.8 


2,800 


40.830 


0.489 


198 


10.70 


219 


12.20 


240 


13.90 


283 


18.1 


327 


23.3 


3,000 


43,740 


0.560 


206 


12.70 


226 


14.30 


246 


16.00 


285 


20.1 


326 


25.0 


3,200 


46,660 


0.638 


215 


14.80 


234 


16.70 


251 


18.30 


288 


22.4 


327 


27.4 



Note. — Bold-face figures indicate point of highest static efficiency. 

The fan tables are based on actual tests made by operating the 
fan at constant speed against different artificial resistances 
consisting of plates, having openings of various sizes, placed at 
the end of a straight pipe about 30 diameters in length. In 
Fig. 147 are shown the performance curves for a multi-blade 
fan, based on the percentage of rated capacity, the latter being 
taken as the point at which the fan operates with the highest 
total efficiency. It should be borne in mind that these perform- 
ance curves are based on a constant speed. 

It is frequently necessary to find the performance of a fan 
at some pressure different from any given in the tables. The 
method of doing this can best be shown by a typical example. 
Assume that 38,000 cubic feet of air per minute is to be delivered 
by a No. 10 Conoidal fan against a static resistance of IJ-^ 
inches. Find the required speed and horsepower. The data for 
1-inch static is given in Table XLVI. The corresponding capac- 

1 From " The Centrifugal Fan," by Frank L. Busey, Trans. A. S. H. & 
V. E., 1915. 



232 



HEATING AND VENTILATION 



ity of the fan at 1-inch static may be found by multiplying by 
the square root of the ratio of 1-inch to IJ^-inch, since we know 
that the pressure varies as the square of the speed and conse- 
quently as the square of the. volume delivered. The capacity on 
a 1-inch basis is thus found to be 34,100 c.f.m. From Table 
XL VI we find that the speed and horsepower for 33,540 c.f.m. 
at 1-inch static are respectively 231 r.p.m. and 9.92 horsepower. 
The speed and horsepower at IJ^ inches static we can compute 
from our knowledge that the speed varies directly as the capacity 
and the power as the cube of the capacity. The fan will deliver 



900 


































/ 


180 
































/ 




IGO 






























/ 






























ite 


,/ 


/' 








|l20 

1)100 


















.^^^ 


f^ 


?5S^ 


il 


/ 








^^ 












t*^. 


^^ 




nt of 


^ 














80 










5^ 


r^ 





^^^ 


/ 






i^ 


^ 


^U. 










=*=^ 










^=,6 


^ 








Tot 


a] Ef 


^cienE^ 


\ 




60 


.^T^- 














^ 


^ 


^ 


a^^ 










■ 


-- 


^ 


fe^/ 


V; 


J' 


'^ 




^ 


^ 






















<^ 





^ 


^ 

































20 



40 



CO 80 100 

Per Cent of Rated Capacity 



120 



140 



160 



Fig. 147. — Performance curves of Niagara conoidal fans. 



38,000 c.f.m. against 134 inches static with a speed of 258 r.p.m. 
and a power consumption of 13.9 horsepower. 

In selecting a fan for a given installation it is usually possible to 
fulfill the required conditions with two or even three different- 
size fans. In such a case the first cost, operating cost, and out- 
let velocities should be considered in making the selection. 
The smaller the fan the greater will be the outlet velocity for 
the same volume. In the case of schools or other buildings where 
quiet operation is essential the outlet velocity should not be 
over about 2200 feet per minute. In industrial buildings, how- 
ever, outlet velocities of about 3000 feet per minute are quite 
permissible. 



DESIGN OF FAN SYSTEMS 233 

209. Correction for Temperature. — The fan tables are based 
on an air density corresponding to a temperature of 70°. In 
a system in which the fan is so located with respect to the heating 
coils that it handles air at a different temperature, a correction 
must be made. This can be done by making use of the relations 
stated in Par. 203. 

For example: Assume that it is required to handle 11,700 c.f.m. 
against a static head of 1% inches at 140°. As brought out in 
Par. 203, at constant capacity and speed, the horsepower and 
pressure vary inversely as the absolute temperature of the air. 
Therefore, if we select a fan which will handle 11,700 c.f.m. 

against a pressure of 1.75 X foq = 1-98 inches at 70°, it will de- 
liver the same quantity against a pressure of 1.75 inches at 140° 
at the same speed. From the fan 
tables we find that a No. 90 steel 
plate fan will do this at a speed of 
403 r.p.m. and a power consumption 
of 7.32 horsepower. The power con- 
sumption at 140° would be 7.32 X 

wr^ = 6.46 horsepower. 

It should be remembered that the 
volume of air fixed by the heating or 
ventilating requirements is usually 
based on the room temperature and yig. 148.— Disc fan. 

the equivalent volume of the same 

weight of air at the temperature at which it enters the fan must 
be found by means of the volume ratios given in Table XXXVI, 
page 176. 

210. Disc Fans. — The disc fan as illustrated in Fig. 148 is well 
adapted for handling considerable quantities of air against very 
low pressures. It is therefore widely used where the air is moved 
into or from a room without passing through a system of ducts. 
While not highly efficient, this type of fan is easily installed, is 
of moderate cost, and requires little space. Such a fan is usually 
inserted directly into a wall or partition and is driven by a 
direct-connected motor. 

211. Heaters. — In a fan system the heat is transmitted from 
the heating units entirely by convection, the air being drawn over 
them at a fairly high velocity. There are two types of heater 




234 



HEATING AND VENTILATION 



used for such work — the cast-iron or ''vento" heater and the 
wrought-iron pipe coil. The former is made up of sections, as 
shown in Fig. 149, connected together at the top and bottom by 

right- and left-hand nipples cast with 
a hexagonal nut at the middle. A 
row of sections thus connected con- 
stitutes a stack. The sections are 
obtainable in nominal lengths of 30, 
40, 50, 60, and 72 inches. All sizes 
are connected at both top and bottom 
and are therefore suitable for hot 
water as well as steam. Vento sec- 
tions are furnished in two widths, the 
''regular'' and the ^'narrow," and by 



It 



the use of nipples of different lengths 
the distance between sections can be 
made either 45^, 5, or 5^^ inches 
center to center, the 5-inch spacing 
being standard. The surfaces are 
broken up by a large number of pro- 
jections which extend into the air 
passages and serve to augment the heating surface in an effec- 
tive manner. The principal dimensions of the sections of 
various sizes are given in Table XL VI I. 



Fig. 149. — Vento heater. 



Table XLVII. — Dimensions of Vento Sections, Inches 




Nominal size 


Square feet 
of surface 


Actual height 


Width 




f30 


8.00 


30 


9H 




40 


10.75 


41^4 


Ws 


Regular width 


50 


13.50 


50%2 


^Vs 




60 


16.00 


601^6 


9M 




[72 


19.00 


72^2 


9M 




40 
50 


7.50 


41^^4 


m 


Narrow 


9.50 


502%2 


QH 




60 


11.00 


601H6 


m 



Approximate weight 8.2 pounds per square foot of surface. 



The method of installing the stacks in a sheet-metal casing 
is shown in Fig. 150. The stacks are staggered so as to break 
up the stream lines and increase the intimacy of the contact 
between the air and the heating surface. The spaces left at the 



DESIGN OF FAN SYSTEMS 



235 



ends of the stacks due to the staggered arrangement are partially 
closed by strips of angle iron. 




Fig. 150. — Vento heater installed in casing. 




© © 






Fig. 151. — Pipe coil heater. 

212. Pipe-coil Heaters. — Heaters made of 1-inch pipes are 
also widely used. The pipe is made into loops with ordinary 



236 



HEATING AND VENTILATION 



elbows, and the loops are screwed into a cast-iron base. The 
base is so partitioned that the steam flows in at one end of each 
of the loops. The sections are arranged as shown in Fig. 151, 
the pipes being staggered with reference to the flow of air 
through the heater. The sections are built in different sizes 
and a wide range in heating surface is available. The complete 
heater is composed of several units in series, as in the case of the 
cast-iron heaters. 

213. Transmission of Heat From Fan-coil Surfaces.^ — The 
heating units are arranged in series, the outside air entering 
the first section and being heated up to the required delivery 
temperature during its passage through the successive sections. 
Since the rate of heat transmission varies nearly as the tem- 
perature difference between the steam and the air, the heat 
transmitted from the last stacks is much less than from those 
with which the cold air first comes into contact. 

The final temperature to which the air is heated depends 
upon the number of stacks through which the air passes in series 
and upon the velocity of the air. The cross-sectional area of the 
heater depends upon the quantity of air delivered, the stacks 
being chosen of sufficient size so that the free area between the 
sections will allow that quantity to pass through at the velocity 
chosen. The free area per section for Vento heaters is given in 
Table XL VIII. Similar data is published by the manufacturers 
of pipe-coil heaters. 



Table 


XLVIII.— Free Areas of Vento Sections 


Size of section, 


Free area, square inches per section 


inches 


b%-in. centers 


5-inch centers 


4^-inch centers 


30 


0.542 


0.460 


0.390 


40 


0.729 


0.620 


0.525 


50 


0.905 


0.768 


0.650 


60 


1.085 


0.921 


0.781 


72 


1.303 


1.104 


0.937 



The velocity to be assumed depends upon the nature of the 
installation. In public buildings and in other places where the 
noise which accompanies high velocities is objectionable, the 
velocity through the heater should be Hmited to between 1000 
to 1300 feet per minute while in factories and similar buildings a 



DESIGN OF FAN SYSTEMS 



237 



Table XLIX. — Final Temperatures and Condensation 

Regular Section — Standard Spacing, 5-inch Centers of Sections — Steam, 

227°, 5 Pounds Gage 



? 


at, 

(S a 

ft '^ 

IS 


Velocity through heater in feet per minute — measured at 70° 


1 


600 


800 


1,000 


1,200 


1,400 


1,600 


1,800 


2,000 


a 


Final 
temp, 
of air 
leav- 
ing 
heater 


Cond. 
lb. per 
sq. ft. 
per 
hour 


f=^ 




Ph 


d 




d 


pR 


d 


fe 




Ph 


d 


fe 


d 




-20 




































-10 


34 


1.69 






























1 





43 


1.65 


38 


1.95 


35 


2.24 


32 


2.46 




















20 


58 


1.46 


54 


1.75 


51 


1.99 


49 


2.23 


47 


2.42 


45 


2.56 


43 


2.65 


42 


2.82 


• 


30 


66 


1.39 


62 


1.64 


60 


1.92 


58 


2.17 


56 


2.33 


54 


2.46 


52 


2.54 


51 


2.69 




-20 


63 


1.60 


55 


1.92 


49 


2.22 


44 


2.46 


40 


2.69 


37 


2.92 


34 


3.12 


31 


3.27 




-10 


69 


1.52 


62 


1.85 


56 


2.12 


51 


2.35 


47 


2.56 


44 


2.77 


41 


2.94 


38 


3.08 


2 





75 


1.44 


68 


1.74 


62 


1.99 


58 


2.23 


54 


2.42 


51 


2.62 


48 


2.77 


46 


2.95 




20 


87 


1.29 


81 


1.57 


76 


1.80 


72 


2.00 


69 


2.20 


66 


2.36 


64 


2.54 


62 


2.69 




30 


93 


1.21 


87 


1.46 


83 


1.70 


79 


1.89 


76 


2.06 


73 


2.21 


71 


2.37 


69 


2.50 




-20 


91 


1.42 


82 


1.74 


75 


2.03 


69 


2.28 


64 


2.51 


59 


2.70 


55 


2.88 


52 


3.08 




-10 


96 


1.36 


87 


1.66 


80 


1.92 


75 


2.18 


70 


2.39 


66 


2.60 


62 


2.77 


58 


2.90 


3 





101 


1.30 


93 


1.59 


86 


1.84 


81 


2.08 


76 


2.27 


72 


2.46 


68 


2.62 


65 


2.78 




20 


110 


1.15 


103 


1.42 


97 


1.65 


92 


1.85 


88 


2.06 


85 


2.22 


82 


2.38 


79 


2.52 




30 


115 


1.09 


108 


1.33 


103 


1.56 


98 


1.75 


94 


1.91 


91 


2.08 


88 


2.23 


85 


2.35 




-20 


114 


1.29 


103 


1.58 


96 


1.86 


90 


2.12 


84 


2.34 


78 


2.51 


74 


2.71 


70 


2.88 




-10 


117 


1.22 


108 


1.51 


101 


1.78 


95 


2.02 


89 


2.22 


84 


2.41 


80 


2.60 


76 


2.76 


4 





121 


1.16 


113 


1.45 


106 


1.70 


100 


1.92 


95 


2.13 


90 


2.31 


86 


2.48 


82 


2.63 




20 


130 


1.06 


122 


1.31 


115 


1.52 


110 


1.73 


105 


1.91 


101 


2.08 


97 


2.22 


94 


2.37 




30 


134 


1.00 


126 


1.23 


120 


1.44 


115 


1.63 


110 


1.80 


106 


1.95 


102 


2.08 


99 


2.21 




-20 


132 


1.17 


122 


1.46 


114 


1.72 


107 


1.95 


100 


2.15 


94 


2.34 


90 


2.54 


86 


2.72 




-10 


135 


1.13 


126 


1.40 


118 


1.64 


111 


1.86 


105 


2.06 


99 


2.24 


95 


2.42 


91 


2.59 


5 





138 


1.06 


129 


1.32 


122 


1.56 


115 


1.77 


109 


1.96 


104 


2.14 


100 


2.31 


96 


2.46 




20 


144 


.95 


136 


1.19 


130 


1.41 


124 


1.60 


119 


1.78 


114 


1.93 


110 


2.08 


107 


2.23 




30 


148 


.91 


140 


1.13 


134 


1.33 


128 


1.51 


123 


1.67 


118 


1.80 


115 


1.96 


112 


2.10 




-20 


146 


1.06 


137 


1.34 


129 


1.59 


121 


1.81 


115 


2.02 


110 


2.22 


105 


2.40 


100 


2.56 




-10 


149 


1.02 


140 


1.28 


132 


1.52 


125 


1.73 


119 


1.93 


114 


2.12 


109 


2.29 


104 


2.44 


6 





152 


.97 


143 


1.22 


135 


1.44 


129 


1.65 


123 


1.84 


118 


2.02 


113 


2.17 


109 


2.33 




20 


156 


.87 


148 


1.10 


142 


1.30 


129 


1.49 


130 


1.65 


126 


1.81 


122 


1.96 


118 


2.09 




30 


159 


.83 


151 


1.04 


145 


1.23 


139 


1.40 


134 


1.56 


130 


1.71 


126 


1.85 


122 


1.97 




-20 


159 


.98 


150 


1.25 


141 


1.47 


134 


1.69 


128 


1.90 


122 


2.08 


117 


2.26 


113 


2.44 




-10 


161 


.94 


152 


1.19 


144 


1.41 


137 


1.62 


131 


1.81 


126 


1.99 


121 


2.16 


117 


2.33 


7 





163 


.90 


154 


1.13 


147 


1.35 


140 


1.54 


135 


1.73 


130 


1.90 


125 


2.06 


121 


2.22 




20 


167 


.81 


159 


1.02 


152 


1.21 


146 


1.39 


lil 


1.55 


136 


1.70 


132 


1.85 


128 


1.98 




30 


169 


.76 


161 


.96 


155 


1.15 


149 


1.31 


144 


1.46 


139 


1.60 


135 


1.73 


132 


1.87 




-20 


168 


.90 


159 


1.15 


151 


1.37 


144 


1.58 


138 


1.77 


133 


1.96 


128 


2.14 


123 


2.29 




-10 


170 


.87 


161 


1.10 


153 


1.31 


147 


1.51 


141 


1.69 


136 


1.87 


131|2.04 


126 


2.18 


8 





172 


.83 


164 


1.05 


156 


1.25 


150 


1.44 


144 


1.62 


139 


1.78 


134 


1.93 


129 


2.07 




20 


175 


.75 


167 


.94 


161 


1.13 


155 


1.30 


150 


1.46 


145 


1.60 


141 


1.74 


137 


1.87 




30 


177 


.71 


169 


.89 


163 


1.07 


158 


1.23 


153 


1.38 


148 


1.51 


144 


1.64 140 


1.76 



238 



HEATING AND VENTILATION 



velocity between 1200 and 1600 feet per minute is permissible. 
For this purpose velocities are based on an air density correspond- 
ing to 70°, this being merely an arbitrary standard adopted for 
convenience in making computations. In very cold climates a 
a velocity of 800 feet per minute or less is advisable because of 
the tendency for the condensation to freeze in the coils. The 
velocity thus chosen is used both as a basis for computing the 
height and width of the heater and also for determining its 
depth, i.e., the number of stacks to be used. In Table XLIX 
are given the final temperatures obtainable from heaters of vari- 

Difforence betw«eu Final Temperature and Initial Temperature of Air 



S °J£ 


o o 


o 


hV^hhh'k 


¥§1 


o o 

§ i 


5 \ 


o o 










































1 












































































































H 


^ = T^^^°^227°Steam 






- 






























'^1 






























! 




























Jri 






jj 






^ 




in 


^ 


^ 




i^I 






















, 


y^ 




s 






^ 






03 




^ 


^ 


^ 


S 


s' 




















^ 


^ 






CO 






00 






M 




w 


ta 


m 


K 


OTJ 


















.^ 










- 






<N 






m 






* 


« 


CD 


'I 


"1 












"^"^ 


^v*- 


b- 






^ 


^ 


.000 




























1 










\ 


< 




^ 






^ 




























1 








^ 




,i?^ 


^ 






X 


000 




























1 
1 




^^ 


S9^ 


'A 


^^i 


f^ 


^ 


^ 




^ 


500 

000 
























''^ 


K- 


-1 


^- 






'^ 


g 


^ 


i!^ 


i 


^ 


^ 







_J_.2( 


O^rr 


i'L 


-- 


^ 


:* 
/ 


^ 


Z> 


y. 


<.-. 


4 






:^ 


^ 

'-'■O' 


/ 

^ 


t 


^ 


^ 


^ 


^' 










900 
800 
700 
600 












^ 










/' 




^ 




^ 


^z 


^^-^ 


























^ 










^ 






.-" 




^ 


■^. 


//^ 


^ 
























^ 






^ 


^ 


' 




^ 


-^ 


^^ 


^ 


''/ 


^ 


>^ 




1 




















^ 






^ 






^ 






-^, 


'^ 




^ 


^ 






\ 
























^ 




^ 




J 






-^ ^ 
































500 


^^ 




^ 




^ 




^ 




^ 




'^-^ 


































^ 




^ 


-^ 




^ 


' _ 






>^ 
































400 


^ 


' 


^ 


^ 


^ 




b 


^ 


y 




































^ 




/ 




^ 




^ 








































300 


^ 


^\ 


-^ 


1> 














































^^ 


-.^^ 




























^. 




















200 


^ 


>^ 




















































>^^ 











































































































1 


^. \ 


3 S 


\ 1 


\ ' 


w 


■^ 


\\ 


?< 


-\ 


i 


-.5. 


§i 


?- 


1 


I- 


5 § 


» u 
1 c 


\^ 


> u 


5^ 


^.^ 


sst 


%^\ 


?s 


§s 


?2 



10.0 

9.0 

8.0 

7.0 

6.0 

5.5 

5.0 

4.5 

4.U 

3.5 

3.0 

2.5 S 

2.0 m 



1.5 



1.0 <^' 
0.9 « 
0.8 d 
0.7 -2 
0.6 S 
0,55 § 
0.5 % 
0.45O 
0.4 ° 
0.35 
0.3 

0.25 

0.2 



Frictional Resistance in Inches of Water 
Fig. 152. — Friction curves for pipe coil heaters. 



ous depths for air at different initial temperatures and velocities. 
The final temperature for which the heater is designed depends 
upon the amount of heat to be supplied and upon whether the 
fan system is to be used for ventilating alone or to supply the 



DESIGN OF FAN SYSTEMS 



239 



heating requirements also. The temperature of the entering air 
used in the computations should be the minimum for which the 
system is to be designed. 

Example. — Assume that a factory is to be heated and that 1,400,000 cubic 
feet of air per hour are required at a temperature of 140°. Minimum out- 
side temperature 0°. What size Vento heater should be used? 

_, , . ^, volume (cubic feet per minute at 70°) 

Free area (square feet) = -, — r- — -7 — -. — — -r 

^ ^ velocity (feet per mmute) 

1,400,000 



Free area 



1200 X 60 X 1.1320 



17.17 square feet 



Difference between Final Temperature and Initial Temperature of Air 

o 0000 O o_o o t^ 00 o °o *o "o °0 




CO to ^ 00 o o o o -< 
Frictional Resistance in Inches of Water 
Fig. 153. — Friction curves for vento heaters. 

Referring to Table XL VIII it is seen that by using eighteen 60-inch 
sections, spaced 5 inches center to center, the free area will be 18 X 
0.921 = 16.58 square feet, which is sufficient, giving a velocity of 1244 
feet per minute. From Table XLIX it is seen that a heater seven stacks 
deep would raise the air from a temperature of 0° to 140° at a velocity 



240 HEATING AND VENTILATION 

of 1200 feet per minute. The heater should therefore be sevnn stacks 
deep. Ordinarily it would be divided into a tempering coil of three stacks 
and a heating coil of four stacks. 

Pipe-coil heaters are chosen in a similar manner from the data 
furnished by their manufacturers. 

Recent tests ^ have shown that the heating effect of both Vento 
and pipe-coil heaters is closely related to the friction loss under- 
gone by the air in passing through them; and that for the two 
different types of heaters, the friction loss will be practically 
identical for the same increase in temperature of the air. This 
might logically be expected as the heat transmission depends upon 
the thoroughness of the rubbing action of the air over the heating 
surfaces. 

From the curves in Figs. 152 and 153 the friction drop can be 
determined for either Vento or pipe coil if the other facts are 
known, and vice versa. These curves are based on the following 
formula which was developed from the results of tests mentioned 
above on pipe coils and upon tests made on Vento heaters by 
L.C. Soule. 

V(h - U) 



c = 



KN 



in which C = condensation in heater — pounds per square foot 
per hour. 
V = velocity of air — feet per minute. 
h — t2 = temperature rise of air. 
A^ = number of stacks in heater. 

K = Si constant = 15,307 for pipe coil and 13,130 for 
Vento. 

As an example of the use of the charts we will take an assumed 
case. With five stacks and an entering temperature of 10°, 
the final temperature for 1200 feet velocity is found from pipe- 
coil data to be 129°, making the increase in temperature 119°. 
In Fig. 152 the horizontal dotted line representing 1200 feet 
velocity intersects the vertical line representing 119° at the point 
A. From point A we draw the 45° line until it intersects the 
vertical line for five stacks. From this point we extend a horizon- 
tal line to the right-hand side of the chart and we see that the 

^ See "Comparison of Pipe Coils and Cast-iron Sections for Warming Air," 
by John R. Allen, Proc. A. S. H. & V. E., 1917. 



DESIGN OF FAN SYSTEMS 



241 



condensation per square foot per hour is 1.89 pounds. The 
frictional resistance is obtained by extending the horizontal Hne 
for 1200 feet velocity to the right until it intersects the diagonal 
line for five stacks; a vertical line from this intersection shows the 
resistance to be 0.25 inches of water. In Fig. 153 the same case 
is worked out for Vento heaters as indicated by the dotted 
lines. The condensation is found to be about 1.94 pounds 
and the velocity 1068 feet for the same resistance and temperature 
rise. It will be noted that while the heating effect and resistance 
of the two heaters are the same, the velocities are quite different. 




Fig. 154. — Piping connections for vento heaters. 



214. Installation and Piping Connections. — The heating units 
are usually mounted on a brick or concrete pier and enclosed by 
a metal duct. The proper arrangement of the steam piping 
connections for Vento heaters is shown in Fig. 154 for a double- 
tier installation. The center section of a long stack is tapped for 
an air vent as shown. Separate valves should be provided for 
each stack or pair of stacks. 

Special care is necessary in arranging the return connections 
from fan heaters, as any accumulation of condensation will soon 

16 



242 HEATING AND VENTILATION 

be frozen by the cold air. There is always a considerable drop 
in pressure through the heaters and the inlet connections, so 
that the pressure at the return connections should not be de- 
pended upon to lift the condensation ; the discharge should be by 
gravity or a vacuum pump should be used. 

Thermostatic control is almost essential on fan systems. The 
diaphragm control valves, similar to those used for radiators, 
are installed as shown in Fig. 154 and are controlled from thermo- 
stats whose expansion member projects into the ducts. 

Problems 

1. In the example in Par. 189, assuming that 657,000 cubic feet of air per 
hour are delivered, if the heat loss as given was computed for 0°, what should 
be the delivery temperature when the outside temperature is 20°? 

2. A factory building is to be heated by a hot-blast system with complete 
recirculation. With the following data given compute the amount of air 
which must be handled per hour by the system. 

Heat loss from building 27,800 B.t.u. per hour per degree 

difference in temperature. 
Inside temperature 65° 

Outside temperature —10° 

Temperature at which 140° 

air is delivered. 

3. In the single duct system of Fig. 140 assume that the longest duct is to 
carry 1100 c.f.m. What is the total pressure required in the plenum 
chamber? 

4. Compute the pipe sizes for a trunk duct system similar to that in Fig. 
141 except that the air quantities in the different sections on a 70° basis are as 
follows: 

Section Air quantity 

A—B 19,000 cf.m. 
B—C 7,500 

C—D 2,000 

B—E 6,000 

E—F 4,000 

Maximum air temperature 130°. 

5. Find the speed, horsepower, and outlet velocity for three different 
sizes of steel plate fan^ delivering 18,000 c.f.m. against a static resistance 
of IH inches at 70°. 

6. Find the speed, horsepower, and outlet velocity for three different sizes 
of multi-blade fan^ delivering 12,000 c.f.m, against a static resistance of 2 
inches at 70°. 

7. A multi-blade fan is to handle 9000 c.f.m. against a static head of l}i 
inches at 140°. What is the required speed and horsepower? 

1 See tables in Appendix, pages 276 to 299. 



DESIGN OF FAN SYSTEMS 243 

8. What would be the size of vento heater required to heat 800,000 cubic 
feet of air per hour from an outside temperature of 10° to a delivery tempera- 
ture of 140°? Assume a velocity through the heater of 1500 feet per 
minute. 

9. What would be the size of vento heater required to heat 1,100,000 cubic 
feet of air per hour from an outside temperature of 0° to a delivery tempera- 
ture of 70°? Assume a velocity through the heater of 1100 feet per minute. 

10. Find by means of the friction chart in Fig. 153 the frictional resistance 
of a vento heater, 5 stacks deep, for a velocity of 1500 feet per minute. Find 
the resistance of a vento heater, 3 stacks deep, for a velocity of 900 feet per 
minute. 



CHAPTER XVI 

AIR WASHERS AND AIR CONDITIONING 

215. The Air Washer. — Various methods of filtering or washing 
air have been in use for many years. In the older forms of 
apparatus the dust was usually filtered from the air by means 
of muslin screens; but this method is not very effective and has 
the disadvantage that the screens soon become clogged with 
dirt, greatly increasing the resistance to the flow of air through 
them. Screen filters have been superseded by the modern air 
washer, in which the dirt is removed from the air by water 
sprays and by the contact of the air against wet surfaces. 

A typical air washer is shown in Fig. 155. It consists of 
three elements — the spray nozzles, the scrubber plates, and the 
eliminator plates. The nozzles are placed in a bank across the 
path of the air and the water is forced through them by a pump 
and is discharged in a fine conical spray or mist in the direction 
of the air flow. The air, drawn through the washer by the fan, 
is thus brought into intimate contact with the water and much 
of the dirt and soluble gases are removed. The final cleansing 
is done by the scrubber plates which are designed to change the 
direction of flow so that the dirt will be thrown out from the air 
by its inertia and by the rubbing of the air over the wet surfaces. 
The plates are kept flooded either by the spray nozzles or by a 
separate row of nozzles placed above them. Following the 
scrubber plates are a series of eliminator plates whose function 
is to remove the entrained water from the air. The lower part 
of the washer constitutes a tank into which the water falls and 
from which it is taken by the circulating pump. A float valve 
admits fresh water as required to replace that evaporated. 

Proper provision must be made in an air washer to prevent 
trouble from the large quantities of dirt which are washed from 
the air and deposited in the tank. A screen of ample area is 
necessary on the suction line to the pump to prevent the dirt 
from being carried into the circulating system, and in some types 
of washers special devices are necessary to enable the spray 

244 



AIR WASHERS AND AIR CONDITIONING 245 




SIDE VIEW 




Suction Strainer Drain' 

END VIEW 

Fig. 155. — Air washer. 



246 HEATING AND VENTILATION 

nozzles to be cleaned periodically by flushing. The accumulated 
dirt must be removed from the tank at frequent intervals. 

The air washer is placed between the tempering coils and the 
heating coils of a fan system, this arrangement being necessary 
in order to insure that the air entering the washer will be at a 
temperature sufficient to keep the spray water from freezing. 

216. Air Conditioning. — The air washer, in addition to cleans- 
ing the air, is also used to add to or reduce its moisture content 
so that the atmosphere in the building will be maintained in 
accordance with the standard fixed by ventilation or manufactur- 
ing requirements. In many textile processes, and in the manu- 
facture of powder, photographic films, etc., the proper ''condi- 
tioning" of the air is of extreme importance. 

Humidification is accomplished by heating the spray water 
so that the air will absorb the proper amount of moisture while 
passing through the spray chamber. Sufficient heat is given 
up by the spray water, first to evaporate sufficient moisture 
to bring the air to saturation at its entering temperature and, 
second, to add further amounts of heat and moisture until the 
air leaves the washer at saturation and at such a temperature 
that it contains the requisite quantity of water vapor. It then 
passes to the heating coils which raise its temperature without 
affecting its moisture content. 

For example, suppose that it is required to deliver air to a 
room at a temperature of 70° and a relative humidity of 60 per 
cent., which requires a moisture content of 4.85 grains per cubic 
foot. We will assume that the outside air has a dry-bulb tem- 
perature of 25° with a relative humidity of 20 per cent. Referring 
to Fig. 156, the entering air is heated by the tempering coils to a 
temperature of 40°, as represented by the line AB. In the washer 
moisture is absorbed from the spray water until the air becomes 
saturated at 40° as represented by BC. Both heat and moisture 
continue to be absorbed from the spray water until the air 
reaches the condition represented by point D, in which it con- 
tains 5.0 grain per cubic foot and has a temperature of 56°. 
It is then heated by the heating coils to the delivery temperature 
of 70°, at which it will have the required relative humidity of 60 
per cent. During this process the moisture content per pound 
of air remains the same, the weight of the vapor per cubic foot 
decreasing slightly because of its expansion due to the tempera- 
ture increase. For approximate calculations this difference may 



AIR WASHERS AND AIR CONDITIONING 247 

be neglected and the line DE representing this last step on the 
chart in Fig. 156 may be taken as a horizontal line. For very 
accurate work the charts in Figs. I and II in the Appendix, which 
are constructed on the basis of 1 pound of air, may be used. 

Every final condition of the air has a corresponding tempera- 
ture at saturation, to which the air is brought before it passes to 
the heating coils. If, in the case given above, the temperature of 
the outside air were above 56° it would be lowered because of the 
heat given up by it to evaporate the moisture which it absorbs — 



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20 5{ 



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20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 
Dxy Bulb Temperature 

Fig. 156. 



provided, however, that its original moisture content be con- 
siderably below saturation. The action would then be repre- 
sented by the line FD. If the dry-bulb temperature of the enter- 
ing air were between 40° and 56° no heat would be added by the 
tempering coil and moisture would be added at a constant dry- 
bulb temperature until the air reached saturation, after which 
it would follow the line CD to 56° as before. 

217. Spray-water Heater. — In order to supply heat to the 
spray water, a heater is installed in the water circulating line, 
usually between the pump and the spray nozzles. If high-pres- 
sure steam is available it is injected directly into the water 



248 



HEATING AND VENTILATION 



through a suitable valve. If low-pressure steam or hot water are 
used a closed heater, in which the spray water circulates through 
tubes surrounded by the heating medium, is necessary. 

218. Humidity Control. — The steam supply valve of the heater 
is controlled — usually by automatic means — so that the proper 
amount of heat is added to the water. In a compressed-air 
system of control, a diaphragm valve is placed on the supply to 
the water heater and may be operated by means of a ''hygrostat" 
or ''humidostat," which corresponds to the thermostat of a 
temperature control system. In place of the thermostatic 
element there is used some material such as wood or hair which 
undergoes a change in length when the moisture content of the 
surrounding air changes. The '^humidostat" is placed either in 



Steam Supply 



Water Inlet 




Fig. 157. — Spray-water heater. 



the main duct or in the principal room of the building and con- 
trols the supply valve on the heater. An injector type of heater 
with a diaphragm control valve is shown in Fig. 157. Another 
and a more rational method of humidity control is based on the 
fact that the air always leaves the washer in a saturated condition 
and therefore its moisture content will depend upon its tempera- 
ture. From a thermostat placed in the path of the air leaving 
the washer the heat added to the spray water is controlled so 
that the exit temperature of the saturated air is at the point 
fixed by the humidity required. In the example given in 
Paragraph 216 the thermostat at the washer outlet would be 
set for 56° and the temperature of the air leaving the washer 
would be maintained at that point. A special duct-type thermo- 
stat of the form shown in Fig. 158 is used for the purpose, 
having a bulb extending into the path of the air and controlling 
the air supply to the diaphragm valve in the usual manner. 
Humidification may also be accomplished by steam jets when no 
washer is used, in which case the jets are located in the same 
position as the washer and may be automatically controlled. 



AIR WASHERS AND AIR CONDITIONING 249 

Another type of humidifier is located directly in the room and 
discharges a finely atomized spray which vaporizes after leaving 
the apparatus. If the steam supply is perfectly free from oil 
and does not possess a disagreeable odor, humidifiers of the type 
which discharge steam directly into the room may be employed. 
They are not always suitable for use in moderate weather, how- 
ever, as a considerable amount of heat is given up by the steam 
which might raise the room temperature to an uncomfortable 
point. The objection to these latter forms of humidifier is the 
absence of automatic means of regulating the humidity. 



I To Diaphragm Valve on Spray Water Heater 




Stem, in Path of Air 



T Air Supply 
Fig. 158. — Duct thermostat for dewpoint method of humidity control. 

219. Cooling and Dehumidification. — If no heat is added to the 
spray water of an air washer some evaporation will still take place 
but the latent heat of the vaporization in this case is taken from 
the air itself. It is by the application of this principle that cool- 
ing by means of an air washer is accomplished, the temperature 
of the air being lowered because of the heat supplied to vaporize 
the added moisture. The extent of the cooling effect depends 
upon the capacity of the entering air for absorbing moisture or, 
in other words, upon the wet-bulb depression of the entering 
air. As the air absorbs moisture in the spray chamber its dry- 
bulb temperature drops but the wet-bulb temperature, which is a 
measure of the total heat of the mixture, remains unchanged. 
If the water is re-circulated its temperature soon drops to the 
wet-bulb temperature. In a perfect washer the dry-bulb tem- 
perature of the air would be reduced to the same point — i.e., 



250 



HEATING AND VENTILATION 



the air would become saturated, but in a commercial washer this 
limit is never reached. The cooling effect actually obtained 
averages about 60 per cent, of the wet-bulb depression, this 
percentage being termed the humidifying efficiency of the washer. 
Referring to the psychrometric chart in Fig. 159, the point A 
represents the original condition of the air at 90° dry-bulb 
temperature and 75° wet-bulb temperature. The cooling and 
humidifying action is represented by the constant wet-bulb 
temperature line AB, the point B representing the final condition 
of 81° dry-bulb temperature. The line AC represents the ac- 



10 



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I 3 



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205*7; 



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50 55 60 65 70 75 
Dry Bulb Temperature 

Fig. 159. 



85 90 95 100 105 



tion if the air were cooled to saturation. The humidifying 

efficiency of the washer is then = ^^ _ „^ = 60 per cent., and 

the amount of moisture actually added is 1.2 grains per cubic foot, 
or approximately 60 per cent, of the 2.0 grains which it would be 
necessary to add to bring the air to saturation. A greater 
cooling effect can be obtained if the spray water be artificially 
cooled, in which case heat will be transferred from the air to 
water by direct contact and no evaporation will take place. 
Both the dry-bulb and the wet-bulb temperatures will fall until 



AIR WASHERS AND AIR CONDITIONING 251 

they coincide at the dew point. If the spray-water temperature 
is sufficiently low they will be reduced still further and some of 
the moisture will be given up by the air. This action is 
represented by the line ADE in Fig. 159. In a properly designed 
washer the air can be cooled to within a few degrees of the 
average water temperature. This method of dehumidification is 
sometimes employed in industrial work. 

The cooling of the spray water is usually accomplished by 
means of a refrigeration plant. The brine coils are placed in the 
tank of the washer so that the spray water during its cycle 
passes over them. If a supply of cold artesian well water is 
available the cost of installation and operation is greatly reduced. 



CHAPTER XVII 
FAN SYSTEMS FOR VARIOUS TYPES OF BUILDINGS 

220. School Buildings. — In school buildings and in various 
other public buildings, the fan system may be designed to furnish 
both the heating and ventilating requirements, or may be used 
to furnish ventilation only, the heating being done by direct 
radiation. In the former case, owing to the necessity for adjust- 
ing the temperature of the air supplied to each individual room, 
a single-duct system is necessary. When ventilation only is 
supplied a trunk-duct system may be used as the air is supplied 
continually at a temperature of about 70°. The arrangement 



Fresh 
Air 
Inlet 



^ Tempering Coils 

7 Air. Washer 



Heating Coils 



Mixing Dampers 




Fig. 160. — Arrangement of single duct system. 

of the fan and heater in a single-duct system is shown in Fig. 160. 
The air passes first through the tempering coils, then through 
the air washer, if one is installed, and to the fan, which forces 
part of it through the reheating coils into the hot-air chamber 
and part of it into the tempered-air chamber. The double 
dampers at the entrance to each duct are controlled from thermo- 
stats in the respective rooms so that the temperature of the 
mixture of hot and tempered air is sufficient to supply the heat 
losses from the room and to maintain it at the proper temperature. 
The volume of air delivered is approximately constant regardless 
of the relative proportions of hot and tempered air. A mixing 
damper is illustrated in Fig. 161. The temperature of the 
tempered air is maintained at about 70° and that of the heated 
air at about 140°. Sometimes this arrangement is varied shghtly 
by running double ducts to the foot of each vertical duct and 
instalHng a mixing damper at that point which is controlled by 
hand through a chain or cable from the room above. 

252 



FAN SYSTEMS FOR BUILDINGS 



253 



Provision must be made for removing the air from the rooms 
at the same rate at which it is suppHed and a system of vent flues 
is provided for that purpose. The flues from the separate rooms 
join together in a trunk duct and lead to a common discharge 
at the roof. The attic is sometimes used as a discharge chamber, 
the flues leading directly to it. Exhaust flues are figured at a 
velocity of 600 to 750 feet per minute and are assumed to carry 
off the same amount of air as is delivered to the room. In some 
cases an exhaust fan is installed to facilitate the removal of the 
foul air. The velocity in the exhaust flues can then be from 1200 
to 1500 feet per minute. In 
public buildings over three or 
four stories in height, where the 
friction in the exhaust flues is 
appreciable, an exhaust fan is 
desirable. The ventilation of 
school rooms is usually done by 
the downward system, the air 
entering near the ceiling and be- 
ing exhausted near the floor. 

221. Factory Heating.— The 
hot4blast system is often the best 
system for most industrial build- 
ings as it affords a, means of 
supplying fresh air to replace 
that containing the fumes or 
moifeture from manufacturing 
processes. It is also desirable in 
factory buildings where the space 

reqiiired by direct radiation cannot be spared. Owing to the 
fact that such buildings are seldom divided into many rooms 
the air can be supplied at a constant temperature through a 
truhk system of ducts. A draw-through arrangement is almost 
universally used, the heating coils being placed on the suction 
side of the fan, which discharges directly into the main duct. 
For ordinary shop buildings of I steel construction, the ducts are 
of galvanized iron and are suspended from the columns or roof 
trusses. An example of this arrangement is shown in Fig. 162. 
In modern reinforced-concrete buildings the columns are fre- 
quently made hollow and used as the air ducts, the heating ap- 
paratus and the trunk duct being located on the roof and ar- 




FiG. 161. — ^Mixing damper. 



254 



HEATING AND VENTILATION 



ranged to discharge the air into the top of each column. Dis- 
charge openings are made in the columns at each floor. The 




trunk duct and branch ducts which are on the roof must be well 
insulated. Details of this method of construction are shown in 



FAN SYSTEMS FOR BUILDINGS 



255 



Fan and Heater 
Located in Pent 
House 
Branch Duct 



Fig. 163. The air is sometimes carried underground in brick 
or concrete ducts, but the heat loss from such ducts is con- 
siderable. 

222. Heating of Theatres and Audi- 
toriums. — Theatres and auditoriums are 
usually both heated and ventilated by 
the fan system. In a theatre the air is 
usually admitted through openings in the 
floor, the space beneath the floor acting 
as a plenum chamber as shown in Fig. 
164, These openings are made adjustable 
so that the distribution of air throughout 
the house can be controlled. The foul 
air is removed through registers near the 
roof and beneath the galleries. An ex- 
haust fan is often provided. If it is not 
possible to introduce the air through the 
floor, registers in the side walls are pro- 
vided for the purpose. The former sys- 
tem provides a much more even distri- FigI 63. -Hollow column 

^ method of distribution. 

bution, however. 

Air washers are installed in all first-class theatres, both to 
remove dust from the entering air and to cool it. Direct radia- 
tion is usually necessary in the lobby, offices, and dressing rooms. 





Fig, 164. — Theatre ventilating system. 

223. Methods of Estimating Heating Requirements. — It is 

frequently necessary to estimate the cost of heating a building 
prior to its construction. It is a very difficult matter to do this 
accurately, first, because of the inaccuracies that are inevitable 
in the computation of the heat losses and, secondly, because of 



256 HEATING AND VENTILATION 

the pronounced effect of the manner in which the firing is done 
and in which the system is handled. 

The most satisfactory method is to compute the theoretical 
heat loss and to apply a factor to allow for the manner in which 
it is believed the plant will be handled. To compute the total 
heat loss from the building, it is necessary to assume the tempera- 
ture at which the building is to be carried and the average outdoor 
temperature. The heat required for ventilation will depend upon 
the amount of air used and the number of hours of use. 

Example. — Given a school building heated with direct radiation and 
equipped with a ventilating system. With the following data furnished, 
what would be the annual fuel cost? 

Heat loss from the building per hour per degree difference in temperature 
between the inside and outside, 12,500 B.t.u., not including ventilation. 
Average outside temperature for heating season, 38°. 
Hours use of building, 8:00 a. m. to 4:00 p. m., 5 days per week. 
Amount of air supplied for ventilating, 40,000 cubic feet per minute. 
Cubic feet of space, 300,000. 

The actual time during which the building is used is 8 hours per day. 
Let us assume that a temperature of 68° is maintained for 10 hours of each 
of the 5 school days or 50 hours per week. Allowing for vacations, we may 
assume that the school is occupied for 32 weeks of the heating season, or 
1600 hours per year. For the remainder of the 8 months or 5760 hours in 
the heating season, the temperature may be assumed to average 50°. The 
heat loss, not including ventilation, would then be as follows : 
12,500 X (68 - 38) X 1600 =^ 600,000,000 B.t.u. 
12,500 X (50 - 38) X 4160 = 623,000,000 B.t.u. 

1,223,000,000 B.t.u. 
The ventilating fan, if properly handled, would be operated only during 
the actual hours of occupancy or 40 hours per week, 1280 hours per year. 
The heat loss from this source would be 

60 X 40,000 X 1280 X 0.019(68 - 38) = 1,750,000,000 B.t.u. 
During the remainder of the time, the air may be assumed to change l}i 
times per hour due to infiltration. 

300,000 X 1.5 X 4480 X 0.019(50 - 38) = 460,000,000 B.t.u. 
The total heat loss is then 3,433,000,000 B.t.u. 

Assume that the coal used contains 13,000 B.t.u and costs $5 per ton. 
For a plant of this nature, operated by efficient help, we may safely assume 
that 65 per cent, of the heat in the fuel is delivered to the building. The 
total annual cost would then be 

3,433,000,000 _^ ^ 
13,000 X 0.65 ^ 2000 ^ "^^ 
This is the estimated cost on a strict basis. It would be well to add about 
10 per cent, for safety, making the final estimate $1116.50. If unskilled 
help were to have been used or other known factors tending to extravagance 
in the use of heat, it might be necessary to increase the strict figure by as 
much as 30 per cent, in extreme cases. 



FAN SYSTEMS FOR BUILDINGS 



257 



224. Heating Requirements of Various Types of Buildings. — 

The variation in the amount of heat used in different types of 
buildings is shown in Table L, which gives data for a number of 
steam-heated buildings in Detroit, Michigan. These buildings 
are all heated from a central station. The heat loss per hour per 
degree difference in temperature is given for each building. It 
will be noticed that the steam consumption per B.t.u. of computed 
heat loss varies greatly for the individual buildings and that the 
average figures for the different classes of buildings are also quite 
different. 



Table L. — Steam Consumption of Buildings at Detroit, Michigan 

Heating Season of 1914-15 
Average Temperature for Heating Season (Oct. 1 to May 31) — 38.9° 





•2 




1 


ftS 


ption 
of in- 
.on 
.1. 1) 


ption 
cubic 

1.2) 


ption 
f com- 
ss 
1.3) 




c3 


d . 


c3 


as 




M 03 o , 
fl 2 03 • • 


§ ^ s -I- 






O-^^ 


a> 


o"-5 


o Js l-i .. 


O ? Q. 


O-t^ rt 




Is 




ft 

a 
6 


a-^ 

CO 


Steam c 

per squ 

stalled 

(Col. 4 


Steam c 
per the 
ft. of s 
(Col. 4 


Steam c 
per B. 
puted ] 
(Col. 4 


OFFICE 
















BUILDINGS 
















Building No. 
















1 


6,524 


549,000 


26,600 


3,091,264 


474 


5,630 


116.2 


2 


2,755 


326,000 


16,000 


2,393,000 


868 


7,330 


149.5 


3 


3,820 


273,000 


13,100 


1,860,676 


487 


6,810 


142.0 


4 


5,280 


367,000 


16,700 


3,563,200 


668 


9,700 


213.5 


5 


15,300 


1,350,000 


65,000 


12,632,048 


825 


9,350 


194.2 


6 


7,940 


584,000 


29,100 


4,942,767 


622 


8,460 


169.8 


7 


50,0003 


3,220,000 


120,000 


34,209,387 


684 


10,630 


285.0 


8 


79,5003 


4,900,000 


205,000 


41,850,000 


527 


8,540 


204.2 


Totals and 
















weighted aver- 
















ages . . 


171,119 


11,569,000 


491,500 


104,542,342 


610 


9,020 


212 . 5 


RETAIL STORE 
















BUILDINGS 
















Building No. 
















1 


1,673 


160,960 


8,715 


627,200 


375 


3,900 


71.9 


2 


1,256 


111,500 


6,400 


364,700 


290 


3,270 


57.0 


3 


16,1003 


2,725,100 


104,000 


7,254,078 


451 


2,660 


69.8 


4 


11,3153 


1,063,100 


42,400 


6,012,348 


531 


5,660 


141.9 


5 


3,864 


403,000 


18,700 


2,110,900 


550 


5,250 


112.9 


6 


2,684 


459,400 


18,400 


987,000 


368 


2,150 


53.6 


7 


4,413 


325,500 


17,700 


1,677,800 


380 


5,140 


94.6 


8 


1,701 


199,000 


8,690 


1,437,600 


843 


7,210 


165.0 


9 


3,632 


613,000 


21,600 


3,133,650 


862 


5,110 


145.0 


10 


2,620 


393,000 


16,500 


1,539,560 


587 


3,910 


93.2 


11 


2,513 


350,000 


11,890 


2,214,200 


880 


6,320 


186.1 


12 


2,162 


197,800 


8,200 


1,072,900 


496 


5,420 


130.8 


Totals and 
















weighted aver- 
















ages 


53,933 


7,001,360 


283,195 


28,431,936 


527 


4,060 


100.5 


RESIDENCES: 








Totals and av- 
















erages for 114 
















buildings 

GARAGES: 
Totals and av- 


65,421 


3,156,800 


304,499 


37,484,000 


573 


11,870 


123.0 
















erages for 12 
















buildings 


11,414 


1,219,700 


74,243 


9,949,800 


870 


8,160 


134.0 



1 B.t.u. per hour per degree difference between inside and outside temperatures. 

2 Including steam for heating water. 

3 Including equivalent of fan coil. 

17 



CHAPTER XVIII 
CENTRAL HEATING 

225. Location of Power Plant. — It is not intended in this 
chapter to discuss the design of heating systems, such as are in- 
stalled for the purpose of heating parts of a city, but rather to 
describe the methods used in distributing heat to groups of build- 
ings such as public institutions; and as the conditions under which 
different systems are installed differ widely, the suggestions 
which follow can be but general. 

Before starting the design of the distribution system it is first 
necessary to have a careful survey made of the property, showing 
the location of the buildings to be heated and the elevation of 
their basements and first floors, together with a general profile 
of the ground through which the tunnels or pipes are to be run. 
The profile of the ground will largely determine the proper loca- 
tion of the power house. In general, the power house should be 
located as nearly as possible to the buildings to be heated or as 
nearly as possible to the largest steam load, but the facilities for 
receiving coal should also be taken into consideration. If it is 
possible to locate the plant On a siding from which coal can be 
delivered direct from the cars to the bunkers without trucking, 
this will often prove to be the most economical arrangement 
even if it necessitates locating the plant at some distance from the 
buildings to be heated ; for the cost of loading, trucking, and un- 
loading will usually overbalance the investment charges on the 
additional length of steam pipes required if the plant is located 
in the more distant location. 

If possible the plant should be so located that the condensation 
from the various buildings can be drained to it by gravity, and 
it should also be located so that the floor of the boiler room can be 
drained to the sewer. Considerable difficulty is usually ex- 
perienced in carrying away the water from the cleaning and 
blowing down of the boilers if no sewer connection can be made. 
The question of the soil, the water supply, and the general appear- 
ance of the power house must also be taken into consideration. 

258 



CENTRAL HEATING 259 

226. Boilers. — The selection of boilers of the proper type and 
size is of extreme importance in the economical operation of 
the plant. A thorough study should be made of the heating and 
electric load, both present and future. The maximum demand 
for steam for heating should be computed on a basis of the ra- 
diation installed plus a liberal allowance for transmission losses. 
The demand for steam due to the lighting and power require- 
ments should be computed from a knowledge of the maximum 
current demand and the steam consumption of the electric 
generating units, allowing also for the energy used by the power- 
plant auxiliaries. The boiler capacity must be such as to fill 
whichever of the two requirements proves to be the greater. 
The exhaust steam should always be utilized insofar as possible 
for heating. When the available exhaust is not sufficient, some 
live steam must be used, while if there is more exhaust steam than 
can be utilized some of it must be discharged to atmosphere. 

After having determined the maximum amount of steam which 
the plant might be called upon to furnish, the size of the boilers 
can be chosen. The steam output per rated boiler horsepower 
varies considerably according to the type of boiler, type of fur- 
nace, etc., but a rough rule for small plants is to assume that 1 
square foot of heating surface in a boiler will evaporate 3 pounds 
of water per hour. The total boiler capacity can then be computed 
upon this basis and it should be divided into units of such sizes 
that the expected range of loads can be handled by operating 
the boilers within their range of highest economy. This can best 
be done by providing a certain boiler or boilers to handle the 
lightest loads which are expected and other boilers to handle 
the average operating load and the maximum load. It is de- 
sirable that there be a sufficient number of boilers in the plant so 
that the largest one can be cut out of service at any time for clean- 
ing or repairs. 

If the boiler pressure to be carried is less than 100 pounds, 
either fire-tube or water-tube boilers may be used. In general, 
for this service fire-tube boilers are very satisfactory, as they 
have large water storage, repairs are easily made, and the boiler 
may be operated at an output considerably beyond its rated 
capacity. 

The principal objection to fire-tube boilers, except those of 
the Scotch marine type, is the large space which they occupy. 
If the boilers are to be operated at pressures much over 100 



260 HEATING AND VENTILATION 

pounds as will usually be the case if electric generating units 
are installed, then only water-tube or Scotch marine boilers 
should be used. 

227. Systems of Distribution — Gravity System. — The com- 
mon method of distributing heat is to pipe the steam to the vari- 
ous buildings and return the condensation to the power house. 
If the elevation of the power plant with respect to the other 
buildings will permit, the condensation may be returned by 
gravity to the boiler and no pumping is necessary. With this 
system any difference in steam pressure between the boiler and 
the extreme point in the piping system will result in a correspond- 
ing elevation of the water level in the return system at the 
extreme point — each pound of pressure difference producing a 
difference in level of 2.31 feet. It is essential, then, that with 
a gravity-return system the difference in pressure between the 
boiler and the extreme point of the piping system be compara- 
tively small. The drop in pressure assumed will determine the size 
of the steam piping. In gravity systems it is usual to allow for 
a drop in pressure of not over 2 pounds between the boiler and the 
extreme end of the system. In some cases the gravity-return 
system has been used over quite an extended area, one building 
so heated being as far as 2500 feet from the boiler, and the system 
has given very good satisfaction. 

In a central heating plant using the gravity-return system, 
unless the steam mains are from 6 to 8 feet above the return 
pipes, it is necessary that the steam condensed in the mains be 
dripped into a separate return Hne and pumped back to the 
boilers, by a pump or a return trap. The pump or trap should 
be of sufficient size to take care of the large amount of conden- 
sation which occurs when the steam is first admitted to the 
cold pipes. By returning the condensation of the mains sepa- 
rately, hammering is avoided and the system can be started 
much more rapidly. 

Gravity-return systems are rarely used where the boiler pres- 
sure exceeds 10 pounds. 

228. Low-pressure Pump Return System. — In a very large 
system where it is difficult to get enough difference in elevation 
between the steam and return mains, or where the drop in pres- 
sure exceeds 2 pounds, it is usual to install a pump return system. 
This will usually be necessary in case any of the buildings 
are piped with a two-pipe vapor system as the difference in 



CENTRAL HEATING 261 

pressure between the main and return is then quite Hable to 
be over 2 pounds. One of the common arrangements is to dis- 
charge the condensation from each building through a trap into 
the return main which carries the water back to a tank in the 
power house. From this tank the water is returned to the 
boilers by means of a pump. The drip from the steam main is 
trapped directly to the return main. 

229. High-pressure System. — Steam is sometimes distributed 
at high pressure and the pressure reduced before entering the 
building piping systems by means of a reducing valve. This 
method has some advantages. Because of the higher pressure, 
the allowable pressure drop in the distributing pipes is greatly 
increased. This, together with the fact that the specific volume 
of the steam is less at the higher pressure, allows the use of much 
smaller pipes in the distribution system and thereby reduces its 
cost. In determining the size of the steam mains, a considerable 
drop may be allowed under maximum conditions, providing the 
pressure at the most distant building is always sufficient to heat 
the building. 

230. Combination of Power and Heating System. — In the 
majority of cases the heating system is combined with an electric 
lighting and power system. The piping connections may be 
made in a manner quite similar to the arrangement in Fig. 97, 
page 140, provision being made to feed live steam to the heating 
mains to supplement the exhaust steam when the latter is less 
than the heating requirements. A back-pressure valve should 
be provided to insure against the building up of an excessive 
pressure in the heating mains. When the heating load is very 
large in comparison with the electrical load, part of the boilers 
can be used as high-pressure boilers and the others can be lower 
priced low-pressure boilers connected directly to the heating lines. 
The desirability of such an arrangement, however, is determined 
entirely by local conditions. 

231. Hot-water Heating. — A hot-water system, using forced 
circulation, is very satisfactory if properly designed. The water 
is heated in a tube heater by the exhaust steam and is circulated 
through the system by means of a centrifugal pump. A vacuum 
can be carried on the engine exhaust to a degree depending upon 
the outgoing temperature of the water. To supplement the 
exhaust steam heater a live steam heater is installed, but in most 
cases it need be operated only in the coldest weather. The 



262 



HEATING AND VENTILATION 



temperature of the outgoing water is adjusted by the operating 
engineer for the prevailing weather conditions in accordance 
with a prearranged schedule. 

The distribution lines in a hot-water system may be arranged 
according to either of two schemes. In the one-pipe circuit 
system a single main makes a complete circuit of the territory 
covered and the supply connection to each building is taken from 
the top of the pipe and the return connection is made to the 
bottom of the pipe a few feet further along and a resistance is 
inserted in the pipe between the connections which has the 
effect of diverting the water into the building system. 

In the multiple or two-pipe system both a flow- and a return- 
main are installed, the water passing from the flow main through 
the building systems and back to the plant via the return main. 
The multiple system is the more commonly used although it is 
somewhat the more expensive to install. 

The systems in the buildings are arranged in the ordinary 
mariner for either system of distribution. 

232. Methods of Carrying Pipes. — The pipe lines serving the 
buildings should always be carried underground if possible. 




Fig. 165. — Wood casing. 



Pipes installed above ground are extremely unsightly and are 
difficult to support and to insulate. Underground pipes may 
be ins'talled either in a small conduit or in a tunnel of walking 
height. The former is a much cheaper method and is quite 
satisfactory when only one or two pipes are to be installed, but 
when a greater number of pipe lines must be provided for or 
when electric cables are also to be installed, a walking tunnel is 
desirable. There are a large number of designs of conduits 
ranging from a rough wooden box to a heavily insulated and 
waterproofed covering. The essential requirements in a conduit 
for heating pipes are — good insulating qualities, protection of the 
pipe from water, provision for free expansion of the pipe, and 
durability. 



CENTRAL HEATING 



263 



A very common form of covering is the wood casing shown in 
Fig. 165. The casing has a wall 4 inches thick and is built of 
segmental staves bound tightly together with steel or bronze wire, 
and the assembled casing is rolled in tar and sawdust to give it a 
waterproof coating and is lined with bright tin to reduce the 
radiation loss from the pipe. Wood is a very good insulator and 
if installed under favorable conditions, this form of conduit is 
very satisfactory. The wood deteriorates, however, if subjected 
to continued dampness. 

The concrete conduit shown in Fig. 166 has the advantage 
of being very durable and is very easily constructed from common 
materials. The concrete prevents any considerable amount of 




Crushed 
Stone 



Fig. 166. — Concrete conduit. 



water from reaching the pipe and if desired can be made nearly 
waterproof by the addition of a waterproofing compound. In 
building this conduit the concrete bottom is first poured and 
allowed to set and then the pipe is installed and covered with 
ordinary pipe covering. The wooden box is then built over it 
and the remainder of the envelope is poured, the sides of the 
trench serving as the outer sides of the form if the soil is suffi- 
ciently cohesive. 

The supports for the pipe in any form of conduit must be such 
as to allow it to move freely when it undergoes a change in length. 
Some form of roller is commonly used and they are placed at 
intervals of 10 or 15 feet. 

Another form of conduit is built of vitrified tile split longitudi- 
nally 'and having insulating material either molded to the walls 



264 



HEATING AND VENTILATION 



of the tile or packed around the pipe. The joints are cemented 
to render them water-tight. Such a conduit is shown in Fig. 167. 
There are many other types of construction in use but those which 



Diatomaceous 
Insulation 




Fig. 167. — Split tile conduit. 

have been described are representative. The heat loss from 
underground lines depends upon the steam temperature, efficiency 
of the insulation, and the soil conditions. Tests made on the 
district heating mains of the Detroit Edison Company in 1913-14, 




Fig. 168.— Slip joint. 

which are laid in conduit of the forms shown in Figs. 165 and 166, 

gave a result of 0.0511 pounds of condensation per square foot 

of external pipe surface per hour for steam at 5 pounds pressure. 

233. Expansion Fittings. — Owing to the length of the pipe 



CENTRAL HEATING 



265 



lines special provision is necessary to take care of the expansion. 
It is seldom feasible to do so by means of bends, and special 
fittings are required. The slip joint illustrated in Fig. 168 is a 
simple means of absorbing large amounts of expansion. It 
consists of a sleeve which is free to move in the body of the fitting, 
a packing gland being provided to prevent leakage. Slip joints 
are located at intervals of from 200 to 300 feet depending upon 
the steam temperature. They must be installed in manholes 
or in some other place where they are accessible for packing. 
The type of expansion fitting shown in Fig. 169 depends upon the 




Outer Ring' 

Fig. 169. — Diaphragm expansion joint. 

flexibility of a copper diaphragm for absorbing the movement 
of the pipe. The advantage of such a fitting is that it requires 
no manhole and does not need to be packed. The amount of 
travel which can be allowed for each fitting is small, the fittings 
being usually placed at intervals of 80 to 100 feet and the pipe 
anchored midway between them. The body of the fitting is also 
anchored and the expansion of the pipe on either side is taken up 
by the diaphragms. The cost of a pipe line fitted with diaphragm 
joints is considerably greater than when slip joints are used. 

234. Installation of Underground Lines. — Careful provision 
should be made for carrying away the ground water from the 
pipe, particularly if the soil is of clay. A drain tile is installed 



266 



HEATING AND VENTILATION 



for the purpose, either directly below or to one side of the con- 
duit and is surrounded with crushed stone or coarse gravel 
extending around the lower part of the conduit. Water seeping 
through to the conduit finds its way into the tile, which carries 
it away to the sewer. Unless this provision is made, the water 
will reach the pipe and will corrode it very rapidly. 

235. Tunnels. — Tunnels of brick or concrete are used when 
several pipes are to be carried. The size and shape of tunnel 
used will depend upon the number of pipes to be carried, the 




Fig. 170. 



character of the soil, and the depth of the tunnel in the ground. 
Fig. 170 shows a small tunnel suitable for pipes of about 8 
inches diameter or less. It is of brick 4 inches thick and has a 
layer of Portland cement on the outside which is painted with 
a thick coat of tar or asphalt over the arch to keep out water. 
Ribs 4 inches thick and 8 inches wide are placed where the sup- 
ports are imbedded in the walls. The supports are of ordinary 
pipe. A drain tile may be placed on either side to carry away 
the ground water but no such provision is necessary if the tunnel 
is built in a sand or gravel soil. Owing to the small size of this 
tunnel and its low head room it is not very suitable for large 
pipes or when much walking through it is necessary. 



CENTRAL HEATING 



267 



In Fig. 171 is shown a larger tunnel of the same general shape. 
It is 6 feet high and 5 feet wide giving ample space for several 
pipes. In Fig. 172 is shown another form of tunnel of still 
larger dimensions. The space under the walkway is used for 
cable ducts. Pipes can be installed on both sides of the tunnel 
if desired. This shape of tunnel is not suitable for use at con- 
siderable depths below the surface because of its flat sides, 
which offer little resistance against earth pressure. The horse- 
shoe shapes previously described should be used in such cases. 



yz to % 




Fig. 171. 



236. Size of Pipes. — The size of steam pipes to be used depends 
upon the amount of steam flowing, the steam pressure, and the 
available pressure drop. If exhaust steam is used the pressure 
drop is limited by the allowable back pressure. In general it is 
necessary to maintain at least 13-^ or 2 pounds pressure at each 
building and in the coldest weather it may be necessary to carry 
a still higher pressure, especially if the piping in the buildings is 
not liberally designed. The required pipe sizes can be deter- 
mined by means of the chart in Fig. 95, page 135, for low-pres- 



268 



HEATING AND VENTILATION 



sure work. In underground piping the noise in the pipes is not 
a factor and advantage can therefore be taken of all of the avail- 
able pressure drop to decrease the size of the pipes. In a high- 
pressure system very much greater pressure drops are permissible 
and the pressure may be allowed to drop, under maximum condi- 
tions, from the boiler pressure nearly to the pressure required for 
heating. It should be borne in mind, however, that the pres- 
sure drop varies as the square of the weight of steam flowing and 




Fig. 172. 



consequently a steam flow slightly greater than that estimated 
will cause a considerably greater pressure drop. It is therefore 
best to allow a reasonable margin in selecting the pipe sizes. 
The chart in Fig. 95 is suitable only for pressures of approxi- 
mately 2 pounds. For higher pressures the capacity of various 
size pipes for a given pressure drop can be found from the basic 
formula of Par. 118. 

For hot- water systems the pipe sizes can be computed by the 
methods given in Chapter X. 



APPENDIX 

Thble I — Coefficients of Heat Transmission Through Building 

Materials 

Walls 

Brick Walls 
Coefficient of heat transmission, (k) B.t.u. per square foot per hour per 
degree difference of temperature. 



Thickness, inches 



Plain 



Plastered on one side Furred and plastered 





k 


k 


k 


4 


0.52 


0.50 


0.28 


8K 


0.37 


0.36 


0.23 


13 


0.29 


■'0.28 


0.20 


■ 17K 


0.25 


■ 0.24 


0.18 


22 


0.22 


0.21 


0.16 


26K 


0.19 


0.18 





Concrete Walls 



Thickness, 
inches 


Plain 


Furred and 
plastered 


Thickness, 
inches 


Plain 


Furred and 
plastered 




k 


k 




k 


k 


2 


0.69 




16 


0.37 


0.24 


4 


0.55 


0.31 


20 


0.33 


0.23 


6 


0.49 


0.30 


24 


0.30 


0.215 


8 


0.47 


0.28 


28 


0.27 


0.20 


10 


0.45 


0.265 


32 


0.25 


0.18 


12 


0.43 


0.25 


36 


0.23 


0.17 



Brick Walls, Sandstone Faces 



Thickness of 
brick, inches 


Thickness of 
sandstone, inches 


k 


Thickness of 
brick, inches 


Thickness of 
sandstone, inches 


k 


4 


4 


0.31 


12 


8 


0.16 


8 


4 


0.22 


4 


12 


' 0.26 


12 


4 


0.17 


8 


12 


0.19 


4 


8 


0.29 


12 


12 


0.15 


8 


8 


0.20 









269 



270 



HEATING AND VENTILATION 



Table I. — Coefficients of Heat Transmission Through Building 

Materials (Continued) 

Walls 

Limestone Walls 



Thickness, inches 


Furred and plastered 


Thickness, inches 


Furred and plastered 




k 




k 


12 


0.49 


28 


0.31 


16 


0.43 


32 


0.28 


20 


0.38 


36 


0.26 


24 


0.35 


40 


0.24 





Tile 


Walls 




Thickness, inches 


Plain tile 


Tile and stucco 


Tile, stucco, and 
plaster 




k 


k 


k 


4 


0.79 


0.75 


0.34 


8 


0.56 


0.54 


0.27 


12 


0.44 


0.41 


0.26 


16 


0.40 


0.37 


0.23 


20 


0.33 


0.31 


0.20 



Wooden Walls 



Clapboard J-^e inch, studding, lath and plaster 

Clapboard J-fe inch, paper, studding, lath and plaster 

Clapboard Jf e inch, sheathing % inch, studding, lath and plaster. 

Clapboard }{q inch, paper, sheathing ^ inch, studding, lath and 

plaster 



k 
0.44 
0.31 
0.28 

0.23 





Miscellaneous Wooden Walls 




Thickness of 
board, inches 


Pine boards only 


Double boards, 
paper between 


Board and corrugated 
iron 




k 


k 


k 


y2 


0.77 


0.32 


0.45 


1 


0.51 


0.24 


0.36 


1^ 


0.43 


0.19 


0.30 


2 


0.35 


0.16 


0.26 


2K 


0.30 


0.14 


0.23 



Inside Partitions:] 

Lath and plaster, one side . . . 
Lath and plaster, both sides . 



k 
0.60 
0.34 



APPENDIX 271 

Table I. — Coefficients of Heat Transmission Through Building 
Materials {Continued) 

Floors 

rioors near ground, assuming ground temperature = 50° 

k 

Cement or tile, no wood above 0.31 

Cement or tile, wood above . 08 

Dirt floor . 23 

Single thickness wood, on joists . 10 

Double thickness wood, on joists . 08 

Ceilings 

k 

Cement or tile, no wood above . 39 

Cement or tile, wood floor above . 10 

Lath and plaster, no floor above . 32 

Lath and plaster, single floor above . 26 

Metal lath and plaster, no floor above . 49 

Roofs 
Metal Roofs: 

k 

Tin on 1-inch sap wood roofing boards : . . . 45 

Copper on 1-inch sap wood roofing boards . 45 

Unlined metal 1 . 30 

Corrugated iron 1 . 50 

Iron over tongue and groove boards . 20 

Iron on wood for framing only. 1 . 32 

Slate Roofs: 

Unlined slate 0.82 

Slate on 1-inch sap wood roofing boards . 43 

Slate over tongue and groove boards . 30 

Slate on wood for framing only . 80 

Tile Roofs: 

Tile % to 1 inch thick 0.80 

Tile on boards . 30 

Miscellaneous : 

Shingles on narrow 1-inch wood strips . 33 

Tar paper on 1-inch sap wood roofing boards . 44 

Tar and gravel over tongue and groove boards . 30 

Roofs 

Miscellaneous {Continued) : 

k 

Six-inch hollow tile, 2-inch concrete, tar and gravel .... . 36 

Same, but with 8-inch tile . 30 

Two-inch concrete, with cinder fill . 80 

Four-inch concrete, with cinder fill 0.60 

Six-inch concrete, with cinder fill . 54 



272 



HEATING AND VENTILATION 



Table I. — Coefficients of Heat Transmission Through Building 

Materials {Continued) 

Windows, Skylights, and Doors 

Average single windows 1 . 09 

Small size windows of ordinary glass 1 . 20 

Single large windows of plate glass 1 . 08 

Double windows . 45 

Single-frame windows with double glass 0. 72 

Single skyhght 1 . 50 

Double skylight 0. 50 

Single monitor 1 . 25 

Doors 



Thickness, 
inches 


Pine 


Oak 


Thickness, 
inches 


Pine 


Oak 


1 


k 

0.56 

. 0.47 

0.41 


k 

0.70 
0.63 
0.58 


2 


k 

0.36 
0.32 
0.27 


k 

0.54 
0.50 
0.43 



Table II. — Thermal Properties of Waters 



Temperature, 
degrees F. 


Specific volume, cubic 
feet per pound 


Density, pounds 
per cubic foot 


Specific heat 


20 


0.01603 


62.37 


1.0168 


30 


0.01602 


62.42 


1.0098 


40 


0.01602 


62.43 


1.0045 


50 


0.01602 


62.42 


1.0012 


60 


0.01603 


62.37 


0.9990 


70 


0.01605 


62.30 


0.9977 


80 


0.01607 


62.22 


0.9970 


90 


0.01610 


62.11 


0.9967 


100 


0.01613 


62.00 


0.9967 


110 


0.01616 


61.86 


0.9970 


120 


0.01620 


61.71 


0.9974 


130 


0.01625 


61.55 


0.9979 


140 


0.01629 


61.38 


0.9986 


150 


0.01634 


61.20 


0.9994 


160 


0.01639 


61.00 


1.0002 


170 


0.01645 


60.80 


1.0010 


180 


0.01651 


60.58 


1.0019 


190 


0.01657 


60.36 


1.0029 


200 


0.01663 


60.12 


1.0039 


210 


0.01670 


59.88 


1 . 0050 


220 


0.01677 


59.63 


1.007 


230 


0.01684 


59.37 


1.009 


240 


0.01692 


59.11 


1.012 


250 


0.01700 


58.83 


1.015 



1 Condensed from Marks and Davis "Steam Tables. 



APPENDIX 273 



PSYCHROMETRIC CHARTS 

The curves in Figs. I and 11^ give the complete properties of air based on 
the pound of air as a unit. The curves in Fig. I are to be used for dry-bulb 
temperatures of from 20° to 110° and those in Fig. II for dry-bulb tempera- 
tures of from 80° to 380°. Having given the wet- and dry-bulb tempera- 
tures of the air, the moisture content in grains per pound of dry air is found 
by passing vertically from the dry-bulb temperature on the horizontal scale 
to the diagonal line corresponding to the wet-bulb temperature and thence 
horizontally to the scale of moisture content at the left. The dew point is 
determined by passing horizontally to the left from the intersection of the 
dr5^-bulb and wet-bulb temperature lines to the saturation curve, the point 
of intersection being the dew point. The heat required to raise the tem- 
perature of 1 pound of air plus its moisture content when saturated, and the 
corresponding vapor pressure are found by passing vertically from the dew 
point to the respective curves and thence to the corresponding scales at the 
left. The total heat is found by passing vertically from the wet-bulb tem- 
perature on the saturation curve to the total heat curve and thence to the 
scale at the left. The volume of air in cubic feet per pound for saturated air 
and for dry air is obtained by passing vertically from the dry-bulb tempera- 
ture to the respective curves and to the scale at the left. 

Example. — Assume dry-bulb temperature = 75° 

relative humidity = 60 per cent. 

From the chart we obtain : 

Wet-bulb temperature, 65.25°; dew point, 60°; grains moisture per pound 
dry air, 77; heat required to raise 1 pound air plus its moisture content when 
saturated at 60° through 1°, 0.247 B.t.u. 

Vapor pressure of air saturated at 60°, 0.523 inches mercury. Total heat 
in 1 pound of air with its moisture content when saturated at 65.25°, 29.75 
B.t.u. 

As to this last quantity, the total heat of saturated air at 65.25° is the 
same as that of the air under the given conditions, 65.25° being the wet-bulb 
temperature. 

^ From "Fan Engineering," Buffalo Forge Company. 



18 



274 



HEATING AND VENTILATION 




OLi osT oei on og' 



APPENDIX 



275 




oozi oon oooT 



OOi 009 OOS 00^ 
iJY Xjq joqi lad ajn^siom jo snitjjf) 



276 



HEATING AND VENTILATION 



STATIC PRESSURE TABLES FOR A. B. C. TYPE S, STEEL PLATE FAN 

CAPACITY TABLE 

Table III. — No. 50 Single Inlet Steel Plate Fan — Type S 







S. P. K" 


S. P. ys" 


S. P. H" 


S. P. rs" 


S. P. %" 


S. P. Vs" 


Vol- 
ume 


ti 














4 


ft 


ft 


ftl 


n 

ft 


ft 


ftl 


B 

ft 


i 


T3 

fts 


B 

ft 


ft 


^ B 

aS! ft 


ft 

-a 


ftl 


a 
ft 


ft 






d^ S" 


« 


m 




Ph 


m 


H^ 


tf 


« 


H^ 


« 


m 


H^ tf 


pq 


H& 


« 


m 


2250 


1000 


2366 


301 


.218 


2690 


343 


.291 


2940 


375 


.365 


3175 


404 


.443 


1 
3400] 433 .523 


i 1 
3610, 460! .610 


2475 


1100 


2490 


317 


.256 


2780 


354 


.337 


3040 


387 


.417 


3267 416 .501 


3480, 443 .585 


3670 468 .675 


2700 


1200 


260C 


331 


.305 


2925 


373 


.390 


3125 


398 


.473 


3360 427 .563 


3575 455 .655 


3763 480 .747 


2925 


1300 


2736 


348 


.360 


3000 


382 


.446 


3237 


412 


.537 


3475! 442 .633 


36751 468| .730 


3865 492 .828 


3150 


1400 


2846 


362 


.418 


3107 


395 


.509 


3310 


422 


.603 


3573i 455i .707 


3750' 478; .808 


3965 505! .914 


3375 


1500 


2987 


381 


.490 


3226 


411 


.586 


3460 


440 


.686 


3650, 465 .790 


3860: 492i .895 


4060 517i;01 


3600 


1000 


313C 


399 


.563 


3350 


427 


.666 


3565 


454 


.770 


3765 480 .880 


3960j 504 .990 


4160 5301.11 


3825 


170C 


32 7C 


416 


.645 


3475 


442 


.755 


3680 


469 


.864 


3885! 495' .978 


4055 5171.10 


4250 5411.22 


4050 


1800 


3410 


434 


.750 


3607 


460 


.855 


3810 


485 


.973 


4010 5101.09 


4180 5331.24 


4350 5541.34 


4275 


190t 


3546 


452 


.838 


3730 


475 


.965 


3935 


501 


1.08 


41201 524|1.21 


4320 5501.34 


4455 5671.46 


4500 


2000 


370( 


471 


.949 


3860 


491 


1.08 


4050 


515 


1.20 


4255 5411.34 


4423; 564'1.47 


4580 5841.61 


4725 


210C 


385f 


490 


1.07 


4000 


51C 


1.21 


421C 


536 


1.33 


4350 5541.48 


4535) 578'l.62 


4680 5961.75 


495C 


220C 


4000 


510 


1.20 


4168 


53C 


1.36 


432C 


550 


1.49 


4500 5731.63 


4670! 595:1.78 


4800 6111.92 


5175 


230( 








4323 


55C 


1.50 


445C 


566 


1.63 


4628i 589|1.79 


4770! 6071.95 


4930 6282.10 


540C 


2400 








4460 


56J 


1.62 


4620 


588 


1.82 


4740i 6041.97 


4920, 626;2.13 


5045 6412.285 


5625 


2500 








4600 


586 


1.83 


472t 


600 


1.99 


48801 622,2.16 


5036! 6412.32 


5170 6582.485 


585C 


260( 














4910 


625 


2.20 


5000 637 2.36 


5180| 660i2.54 


5325 6782.700 


630( 


2800 














518C 


66C 


2.62 


5280! 67li2.81 


5435 692 2.98 


5510 702 3.180 


6750 


3000 














5485 


698 


3.09 


56101 7143.31 

1 1 


5650 720j3.48 


5840i 7443.692 







S. P. 1" 


S. P. IM" 


s. P. IM" 


S. P. 1%" 


S. P. 2" 


S. p. 2yi" 


Vol- 


_« 


























ume 


?-s 


73 


B 




73 


B 




t3 


B 




Ti 


a 


ft 


T) 


a 




-r, ' 


a ft 




u > 


af. 


ft 


JS 


ft^> 


ft 


J3 


ftfl) 


ft 


^ 


ftll^ 


ft 


^ 


ftS 


ft 


-C 


ft^ 


ft -c 






H& 


tf 


pq 


C ft 


« 


« 


H g* 


rt 


pq 


H& 


tf 


m 


H& 


« 


m 


H^ 


rt pq 


2700 


1200 


3955 503 


.850 


4152 


529|l.04 


4470 5701.26 


4950 


630 


1.48 


523o' 6671.72 


5750 732'2.22 


2925 


1300 


40501 515 


.927 


4380 


558;1.13 


4550, 5801.35 


5024 640 


1.59 


5295 673! 1.83 


5820 740 2.34 


3150 


1400 


4143 5271.02 


4465 


5691.24 


4700! 5981.46 


5105! 650 


1.70 


5350 6811.97 


5900 752 2.49 


3375 


1500 


4250 5411.12 


4570 


5821.33 


4850^ 61711.58 


51801 660 


1.83 


5450 694 2.09 


5950 757 2.64 


3600 


1600 


4325! 550)1.22 


4652 


594:1.47 


4950i 630ll.71 


5245! 667 


1.96 


5550; 707:2.23 


6025 7672.80 


3825 


1700 


4437, 5641.34 


4750 


6051.61 


5040 6421.85 


5330 679 


2.11 


5625 7172.38 


61001 7772.96 


4050 


1800 


4527 5761.47 


4846 


6161.73 


5110 6521.99 


5410 


689 


2.28 


57001 725 2.55 


61951 7883.15 


4275 


1900 


4613 5881.60 


4945 


6301.87 


5230' 66612.14 


5520 


702 


2.44 


5780! 737i2.73 


626.51 798i3.33 


4500 


2000 


4743: 6041.75 


.5075 


646 2.03 


5325! 678,2.32 


5620 


715 


2.62 


5860; 746 2.92 


6365 810|3.53 


4725 


2100 


4850, 618,1.89 


5145 


655:2.19 


5440 693 2.49 


5724 


729 


2.81 


5955 759 3.12 


6475 825 3.76 


4950 


2200 


4970 633 2.07 


5256 


6702.365 


5550; 7072.68 


5790 


738 


3.00 


6050i 7693.32 


6550 8354.00 


5175 


2300 


5090 648 2.345 


5370 


684 2.565 


56301 7172.88 


5900 


751 


3.22 


61501 783 3.54 


6610! 8444.24 


5400 


2400 


5210 663 2.447 


548C 


698 2.770 


57501 73213.09 


6025 


767 


3.44 


62701 798,3.78 


67001 853 4.50 


5625 


2500 


5340 6802.655 


5610 


7152.970 


5850 745 3.32 


6100 


776 


3.67 


6343: 8084.04 


6800 8654.76 


5850 


2600 


5485 698 2.875 


5740 


7313.22 


5980 762 3.56 


6200 


79C 


3.92 


3460 823 4.31 


6880 877 5.04 


6300 


2800 


5710 727 3.390 


5960 


7.593.715 


6230! 79414.09 


6460 


822 


4.48 


66501; 8474.86 


7090 903 5.65 


6750 


3000 


5970> 7603.890 


6200 


7904.28 


6460! 82214.68 


6675! 850 


5.07 


6900 8795.49 


7295 928 6.32 


7200 


3200 


6230 794 4.480 


6475 


8254.91 


6730 857i5.34 


6920 881 


5.74 


7135 909 6.17 


75301 960 7.02 


7650 


3400 


6580 8385.180 


6740 


8585.62 


6960 886 6.06 


7150! 910 


6.51 


73551 937 6.93 


7750 9877.83 


8100 


3600 


6815 870 5.900 


7000 


8946.37 


7200 916i6.85 


7440 


948 


7.30 


7600 968 7.78 


802010218.69 


8550 


3800 


7105 905 6.730 


7350 


936 7.25 


7475 952 7.72 


7660 


976 


8.21 


78401 999 8.67 

1 


82201047,9.68 



APPENDIX 



277 



CAPACITY TABLE 

Table IV. — No. 60 Single Inlet Steel Plate Fan — Type S 







S 


P. 


K" 


S 


P. 


Vs" 


S 


P. 


y2" 


S 


P. ys" 


S 


P. 


H" 


S 


P. Vs" 


Vol- 
ume 




































It 


a1 


a 






B 
d 


d 




6 
d 


d 


'V 

a?. 


d 


d 


13 


a 

d 


d 




a 

d 


d 

43 






H& 


W 


m 


H& 


P^ 


PQ 


H& 


Ph 


M 


H& 


f« 


w 


H& 


tf 


m 


H& 


P5 


m 


3200 


1000 


2366 


251 


.287 


2690 


286 


.415 


2940 


312 


.519 


3175 


337 


.630 


3400 


361 


.743 


3610 


383 


.868 


3520 


HOC 


2490 


264 


.365 


2780 


295 


.478 


3040 


323 


.593 


3267 


347 


.712 


3480 


370 


.832 


3670 


390 


.960 


384(1 


1200 


2600 


276 


.435 


2925 


311 


.554 


3125 


332 


.673 


3360 


356 


.800 


3575 


379 


.932 


3763 


400 


1.06 


416C 


1300 


2736 


290 


.512 


3000 


319 


.635 


3237 


344 


.762 


3475 


369 


.900 


3675 


390 


1.04 


3865 


410 


1.18 


448C 


1400 


2846 


302 


.595 


3107 


330 


.730 


3310 


351 


.858 


3573 


379 


1.00 


3750 


398 


1.15 


3965 


421 


1.30 


480C 


1500 


2987 


317 


.697 


3226 


343 


.833 


3460 


367 


.977 


3650 


388 


1.12 


3860 


410 


1.27 


4060 


431 


1.43 


512C 


1600 


3130 


332 


.800 


3350 


356 


.948 


3565 


379 


1.09 


3765 


400 


1.25 


3960 


420 


1.41 


4160 


441 


1.57 


544C 


170(1 


3270 


347 


.917 


3475 


369 


1.07 


3680 


391 


1.23 


3885 


413 


1.39 


4055 


431 


1.56 


4250 


451 


1.73 


576C 


1800 


3410 


362 


1.07 


3607 


382 


1.21 


3810 


405 


1.38 


4010 


425 


1.55 


4180 


443 


1.76 


4350 


462 


1.92 


fi08f 


190(1 


3546 


377 


1.19 


3730 


396 


1.37 


3935 


418 


1.54 


4120 


437 


1.72 


4320 


458 


1.90 


4455 


473 


2.08 


6400 


200C 


3700 


393 


1.35 


3860 


41C 


1.53 


4050 


430 


1.71 


4255 


452 


1.91 


4423 


470 


2.09 


4580 


487 


2.29 


6720 


210C 


3850 


408 


1.52 


4000 


425 


1.72 


4210 


447 


1.89 


4350 


462 


2.11 


4535 


481 


2.31 


4680 


498 


2.49 


704C 


2200 


400C 


425 


1.70 


4168 


443 


1.93 


4320 


458 


2.12 


4500 


478 


2.32 


4670 


497 


2.53 


4800 


5102.73 


736C 


2300 








4323 


459 


2.13 


4450 


473 


2.33 


4628 


491 


2.55 


4770 


507 


2.77 


4930 


523 


2.99 


768C 


2400 








4460 


473 


2.31 


4620 


490 


2.59 


4740 


504 


2.80 


4920 


522 


3.03 


5045 


537:3.25 


800C 


2500 








4600 


488 


2.60 


4720 


502 


2.83 


4880 


518 


3.07 


5036 


534 


3.30 


5170 


5493.53 


832t 


2600 














4910 


521 


3.13 


5000 


531 


3.36 


5180 


550 


3.61 


5325 


5653.84 


8960 


2800 














5180 


550 


3.71 


5280 


560 


3.99 


5435 


578 


4.23 


5510 


5854.53 


9600 


3000 














5485 


582 


4.40 


5610 


596 


4.71 


5650 


600 


4.96 


5840 


620 


5.25 







S. P. 1" 


S. P. l>i". 


S. P. IK" 


S. P. IM" 


S. P. 2" 


S. 


P. 2M" 


Vol- 


^ 


































ume 


31 




l!i 


a1 


a 

d 


d 

,£3 


a1 


a 

d 


d 


a1 


a 

d 


d 


-d 
a^ 


a 

d 


d 


73 
an) 


a 

d 


d 






^& 


pi 1 pq 


H& 


rt 


m 


h& 


rt 


m 


H& 


tf 


W 


'C a 


rt 


pq 


t-l CO 


rt 


pq 


3840 


1200 


3955 


420 


1.21 


4152 


4.,2 


1.48 


4470 


475 


1.79 


4950 


525 


2.10 


5230 


555 


2.44 


5750 


610 


3.16 


41 6C 


13O0 


4050 


430 


1.32 


4380 


465 


1.61 


4550 


483 


1.92 


5024 


533 


2.26 


5295 


561 


2.61 


582C 


617 


3.33 


448C 


140C 


4143 


439 


1.45 


4465 


474 


1.76 


4700 


499 


2.08 


5105 


542 


2.43 


5350 


568 


2.80 


5900 


626 


3.54 


480C 


1500 


4250 


451 


1.59 


4570 


485 


1.91 


4850 


515 


2.25 


5180 


550 


2.61 


5450 


578 


2.97 


595C 


631 


3.76 


512C 


1600 


4325 


459 


1.74 


4652 


495 


2.09 


4950 


526 


2.43 


5245 


557 


2.78 


5550 


589 


3.18 


6025 


640 


3.98 


5440 


1700 


4437 


471 


1.91 


4750 


504 


2.29 


5040 


534 


2.63 


5330 


566 


3.01 


5625 


598 


3.39 


6100 


648 


4.22 


576C 


1800 


4527 


481 


2.08 


4846 


514 


2.46 


5110 


542 


2.83 


5410 


574 


3.24 


5700 


605 


3.63 


6195 


658 


4.48 


6080 


1900 


4613 


490 


2.27 


4945 


525 


2.66 


5230 


555 


3.05 


5520 


586 


3.47 


5780 


613 


3.89 


6265 


665 


4.74 


6400 


2000 


4743 


504 


2.48 


5075 


538 


2.89 


5325 


565 


3.29 


5620 


597 


3.73 


5860 


621 


4.16 


6365 


676 


5.03 


672C 


210(1 


485(1 


515 


2.69 


5145 


545 


3.12 


5440 


578 


3.55 


5724 


607 


4.00 


5955 


632 


4.43 


6475 


687 


5.35 


704(1 


220C 


497C 


528 


2.94 


5256 


558 


3.37 


5550 


589 


3.81 


5790 


615 


4.28 


6050 


642 


4.72 


655C 


695 


5.68 


736C 


230C 


509C 


540 


3.33 


5370 


57(1 


3.65 


5630 


598 


4.09 


5900 


626 


4.58 


6150 


653 


5.05 


661C 


701 


6.03 


7680 


2400 


521C 


553 


3.48 


5480 


583 


3.93 


5750 


610 


4.39 


6025 


640 


4.90 


627(1 


666 


5.38 


670C 


711 


6.40 


8000 


2500 


534C 


567 


3.78 


5610 


595 


4.23 


5850 


621 


4.72 


610C 


649 


5.22 


6343 


674 


5.74 


6800 


722 


6.77 


8320 


2600 


5485 


582 


4.09 


5740 


60£ 


4.58 


5980 


635 


5.07 


620C 


658 


5.57 


6460 


686 


6.13 


6880 


730 


7.17 


8960 


2800 


5710 


606 


4.82 


5960 


632 


5.28 


6230 


661 


5.83 


646C 


686 


6.37 


665C 


706 


6.91 


7090 


752 


8.04 


9600 


3000 


5970 


633 


5.54 


6200 


658 


6.08 


6460 


686 


6.67 


6675 


698 


7.23 


690t 


732 


7.82 


7295 


773 


8.98 


10240 


3200 


6230 


662 


6.37 


6475 


687 


6.98 


6730 


715 


7.58 


692C 


735 


8.17 


7135 


757 


8.80 


7530 


799 


9.98 


1088C 


340t 


mi. 


698 


7.36 


674(1 


715 


8.00 


696C 


73C 


8.62 


71 5(1 


76(1 


9.26 


7355 


781 


9.87 


7750 


823 


11.14 


1152C 


360C 


6815 


723 


8.40 


7000 


745 


9.09 


7200 


764 


9.75 


744f 


790 


10.39 


760C 


807 


11.08 


8020 


851 


12.37 


12160 


3800 


7105 


755 


9.58 


7350 


780 


10.32 


7475 


793 


10.98 


7660 


814 


11.67 


7840 


832 


12.33 


8220 


873 


13.78 



278 



HEATING AND VENTILATION 



CAPACITY TABLE 

Table V. — No. 70 Single Inlet Steel Plate Fan — Type S 







s. p. 


H" 


S 


P. 


H' 


g 


P. 


H" 


■ s. P. ys" 


s 


P. 


K" 


S. P. Vs" 


Vol- 
ume 






























^-i 


"O 


a 


d 


t: 


a 


d 


'S 


B 


d 


J 


a 


a 


"^ 


a 


d 


7 


a 






o > 


an''. 


a 


JS 


a^, 


a 


rfl 


a!^> 


ft 


pC 


a)^. 


a 


nC 


ail'. 


a 


JS 


a^. 


a 


ji 






H& 


rt 


ffl 




P^ 


m 


H& 


Pi 


pq 


H CD 


rt 


« 


Hg 


« 


m 


^g 


Ph 


PQ 


4160 


1000 


2366 


215 


.402 


2690 


245 


.538 


2940 


267 


.674 


3175 


288 


,818 


3400 


309 


.965 


361ol 328 1.13 


4576 


1100 


2490 


228 


.474 


2780 


253 


.622 


3040 


276 


.771 


3267 


297 


.925 


3480 


316 


1.08 


3670 334 1.25 


4992 


1200 


2600 


236 


.565 


2925 


266 


.719 


3125 


284 


.873 


3360 


305 


1.04 


3575 


325 


1.21 


3763 342 1.38 


5408 


1300 


2736 


249 


.665 


3000 


273 


.825 


3237 


294 


.992 


3475 


316 


1.17 


3675 


334 


1.35 


3865 351 1.53 


5824 


1400 


2846 


258 


.773 


'^107 


283 


.944 


3310 


301 


1.11 


3573 


325 


1.30 


3750 


341 


1.49 


3965 361 1.68 


624C 


1500 


2987 


271 


.905 


3226 


293 


1.08 


3460 


315 


1.27 


3650 


332 


1.46 


3860 


351 


1.65 


4060 370 1.86 


6656 


1600 


3130 


285 


1.04 


3350 


305 


1.23 


3565 


324 


1.42 


3765 


341 


1.62 


3960 


359 


1.83 


4160 379 2.04 


7072 


1700 


3270 


297 


1.19 


3475 


316 


1.39 


3680 


335 


1.60 


3885 


353 


1.81 


4055 


369 


2.03 


4250 386 2.25 


7488 


1800 


3410 


310 


1.39 


3607 


328 


1.58 


3810 


346 


1.79 


4010 


365 


2.01 


4180 


380 


2.28 


4350 396 2.49 


7904 


1900 


3546 


323 


1.55 


3730 


339 


1.78 


3935 


357 


1.99 


4120 


375 


2.23 


4320 


393 


2.47 


4455 4051 2.70 


8320 


2000 


3700 


336 


1.75 


3860 


351 


1.99 


4050 


368 


2.22 


4255 


387 


2.48 


4423 


402 


2.72 


4580i 417! 2.97 


8736 


210C 


3850 


350 


1.97 


4000 


364 


2.23 


4210 


383 


2.46 


4350 


396 


2.73 


4535 


413 


2.99 


4680: 426, 3.24 


9152 


2200 


4000 


364 


2.21 


4168 


379 


2.50 


4320 


393 


2.75 


4500 


410 


3.02 


4670 


425 


3.29 


4800; 436 3.55 


9568 


2300 








4323 


393 


2.77 


4450 


405 


3.02 


4628 


421 


3.30 


4770 


433 


3.60 


4930: 4481 3.88 


9984 


240(: 








4460 


406 


2.99 


4620 


420 


3.36 


474(1 


43(1 


3.63 


4920 


447 


3.93 


5045 459 4.22 


10400 


2500 








1600 


418 


3.37 


4720 


430 


3.68 


4880 


443 


3.99 


5036 


458 


4.28 


5170 470 4.59 


10816 


260f 














4910 


446 


4.07 


5000 


455 


4.37 


5180 


471} 4.69 


5325' 483! 4.98 


11648 


?m) 














5180 


471 


4.82 


5280 


480 


5.19 


5435 


491 


5.50 


5510 501 5.88 


12480 


3000 














5485 


499 


5.71 


5610 


511 


6.12 


5650 


514 


6.43 


5840| 530j 6.82 







S. P. 1" 


S. 


P. 1 


Vi" 


S. 


P. W^" 


S. 


P. \y^" 


S. P. 2" 


S. P. 2M" 


Vol- 


.2 














































ume 




T3 


a 

a 


d 


al 


a 

d 


d 


-0 


a 

d 


d 


73 

a$ 


a 

d 


d 


73 
0,% 


a 

d 


d 

A 


.1 


a 

d 


d 








rt 


pq 


H^ 


« 


pq 


H CO 


P^ 


pq 


H^ 


^ 


pq 


H^ 


tf 


pq 


H^ 


P5 


pa 


4992 


1200 


3955 359 


1.57 


4152 


378 


1.92 


4470 


407 


2.33 


4950 


450 


2.72 


5230 


475 


3.17 


575o' 523 


4.11 


5408 


1300 


4050) 368 


1.71 


4380 


398 


2.09 


4550 


415 


2.50 


5024 


457 


2.93 


5295 


481 


3.39 


5820| 529 


4.32 


5824 


1400 


4143! 376 


1.88 


4465 


406 


2.28 


4700 


427 


2.71 


5105 


465 


3.15 


5350 


487 


3.63 


5900 536 


4.59 


6240 


1500 


42501 386 


2.07 


4570 


416 


2.48 


4850 


441 


2.91 


5180 


471 


3.38 


54.50 


495 


3.86 


5950' 541 i 4.88 


6656 


1600 


4325 


393 


2.26 


4652 


424 


2.71 


4950 


450 


3.15 


5245 


476 


3.61 


5550 


505 


4.13 


6025! 5481 5.17 


7072 


1700 


4437 


404 


2.47 


4750 


432 


2.97 


5040 


459 


3.42 


5330 


484 


3.90 


5620 


511 


4.41 


6100 5551 5.47 


7488 


1800 


4527 


412 


2.70 


4846 


440 


3.19 


5110 


465 


3.67 


5410 


494 


4.21 


5700 


519 


4.72 


6195 563! 5.82 


7904 


1900 


4613 


420 


2.95 


4945 


449 


3.45 


5230 


475 


3.96 


5520 


502 


4.52 


5780 


525 


5.05 


6265! 570 6.15 


8320 


2000 


4743 


430 


3.22 


5075 


461 


3.75 


5325 


484 


4.28 


5620 


511 


4.84 


5860 


533 


5.40 


6365 579 6.52 


8736 


2100 


4850 


441 


3.50 


5145 


468 


4.05 


5440 


494 


4.61 


5724 


521 


5.20 


5955 


541 


5.76 


64751 588 


6.95 


9152 


2200 


4970 


452 


3.81 


5256 


477 


4.37 


5550 


505 


4.96 


5790 


527 


5.55 


6050 


550 


6.13 


6550; 595 


7.38 


9568 


2300 


5090 


463 


4.33 


5370 


488 


4.74 


5630 


512 


5.32 


5900 


536 


5.95 


6150 


560 


6.55 


66101 601 


7.82 


9984 


2400 


5210 


474 


4.52 


5480 


498 


5.11 


5750 


523 


5.70 


6025 


547 


6.36 


6270 


570 


6.98 


6700 610 


8.32 


10400 


2.500 


5340' 485 


4.91 


5610 


510 


5.49 


5850 


532 


6.13 


6100 


555 


6.78 


6343 


575 


7.46 


6800! 618 


8.80 


10816 


2600 


5485 


498 


5.32 


5740 


522 


5.95 


5980 


544 


6.58 


6200 


564 


7.23 


6460 


587 


7.96 


68801 625 
7090 644 


9.32 


11648 


2800 


5710 


520 


6.26 


5960 


542 


6.85 


6230 


567 


7.57 


6460 


587 


8.28 


6650 


605 


8.98 


10.44 


12480 


3000 


5970 


542 


7.19 


fi200 


564 


7.90 


6460 


598 


8.66 


6675 


607 


9.38 


6900 


627 


10.13 


7295' 663 


11.65 


13312 


3200 


62.30 


567 


8.27 


6475 


588 


9.07 


6730 


612 


9.86 


6920 


629 


10.60 


7135 


648 


11.40 


7530 68512.97 


14144 


3400 


6580 


598 


9.58 


6740 


613 


10.38 


6960 


632 


11.19 


7150 


650 


12.00 


7355 


670 


12.81 


7750i 705 


14.46 


14976 


3600 


6815 


620 


10.88 


7020 


638 


11.77 


7200 


655 


12.66 


7440 


67613.48 


7600 


691 


14.38 


8020 729 


16.04 


15808 


3800 


7105 


64612.43 


7350 


668 


13.40 


7475 


m 


14.25 


7660 


69715.14 


7840 


713 


16.00 


8220 747 


17.88 



APPENDIX 



279 



CAPACITY TABLE 

Table VI. — No. 80 Single Inlet Steel Plate Fan — Type S 







S. P. 


K" 


S. P. 


%" 


S. P. V2" 


S. P. %" 


S. P. M" 


S. P. %" 


Vol- 
ume 


4J 


















3'aj 


y^ 


a 


ft 


"^ 


a 


ft 


'? 


a 


a 


'^ 


a 


ft 


73 


a 


ft 


T3 


a 


ft 




n s 


aS 


ft 


Si 


ftS 




,0 


ftS^ 




r^ 


0.% 




,£3 


Q,l 


ft 


j^ 


ftfl-, 


ft 


Si 






H^ 


rt 


m 


r-' (c 


Ph 


pq 


H^ 


Ph 


m 


H ^ 


Ph 


m 


H M 


rt 


P5 


HS^ 


PI 


m 


5050 


1000 


2366 


189 


.488 


2690 


214 


.654 


2940 


234 


.818 


3175 


253 


.994 


3400 


271 


1.17 


3610 


288 


1.37 


5555 


HOC 


249(1 


198 


.575 


278(1 


222 


.755 


3()4( 


242 


.935 


3267 


26( 


1.12 


348( 


277 


1.31 


367(1 


292 


1.52 


6060 


1200 


2600 


207 


.685 


2925 


233 


.873 


3125 


249 


1.06 


336C 


268 


1.26 


3575 


285 


1.47 


3763 


300 


1.68 


6565 


1300 


2736 


218 


.80S 


3000 


239 


1.002 


3237 


257 


1.21 


3475 


276 


1.42 


3675 


292 


1.63 


3865 


308 


1.86 


7070 


1400 


2846 


227 


.940 


3107 


248 


1.144 


331( 


264 


1.35 


3573 


285 


1.58 


375C 


299 


1.81 


3965 


316 


2.05 


7575 


1500 


2987 


238 


1.097 


3226 


257 


1.314 


346( 


276 


1.54 


3650 


291 


1.77 


386(] 


307 


2.01 


4060 


324 


2.26 


8080 


160C 


313C 


25C 


1.26c 


3350 


267 


1.497 


3565 


284 


1.73 


3765 


298 


1.97 


3960 


315 


2.22 


4I6O! 332 


2.48 


8585 


170C 


3270 


261 


1.445 


3475 


277 


1.695 


3680 


293 


1.94 


3885 


31C 


2.19 


4055 


323 


2.47 


4250 339 


2.74 


9090 


1800 


3410 


272 


1.686 


3607 


287 


1.920 


381( 


303 


2.18 


4010 


319 


2.44 


4180 


333 


2.77 


4350 


347 


3.02 


9595 


1900 


3546 


283 


1.878 


3730 


297 


2.165 


3935 


313 


2.42 


4120 


328 


2.71 


4320 


344 


3.00 


4455 


35C 


3.28 


10100 


2000 


3700 


295 


2.150 


3860 


305 


2.425 


4050 


322 


2.71 


4255 


339 


3.01 


4423 


353 


3.31 


4580 


365 


3.61 


10605 


2100 


3850 


307 


2.400 


4000 


319 


2.71 


4210 


335 


2.99 


1350 


347 


3.33 


4535 


361 


3.64 


4680 


373 


3.94 


11110 


220(1 


4000 


m 


2.688 


4168 


332 


3.04 


432(1 


344 


3.34 


4500 


358 


3.67 


4670 


372 


4.00 


480(1 


383 


4.32 


11615 


2300 








4323 


345 


3.36 


4450 


354 


3.67 


4628 


369| 4.02 


4770 


380 


4.37 


4930 


393 


4.71 


12120 


24(){) 








4460 


356 


3.63 


462(1 


368 


4.08 


4740 


378 4.42 


4920 


393 


4.78 


5045 


402 


5.12 


12625 


2500 








4600 


367 


4.10 


472C 


376 


4.47 


4880 


389 4.85 


5036 


401 


5.20 


5170 


412 


5.57 


13130 


2600 














491C 


392 


4.94 


5000 


398 5.30 


5180 


413 


5.69 


5325 


423 


6.06 


14140 


2800 














5180 


413 


5.85 


5280 


421! 6.30 


5435 


433 


6.67 


5510 


439 


7.14 


15150 


3000 














5485 


437 


6.93 


5610 


447 7.42 


5650 


450 


7.81 


5840 


465 


8.28 







S. P. 1" 


S. P. IK" ■ 


S. P. ly/' 


S. P. ni" 


S. P. 2" 


S. P. 2y2" 


Vol- 
ume 


1. 

^1 














1^ 


a 


ft 


? 


a 


ft 


"? 


a 


ft 


'? 


a 


ft 


"? 


a 


ft 


'? 


a 


ft 




fti 


ft 


Si 


fti 


ft 


Si 


fti 


ft 


Si 


ftS 


ft 


Si 


fti 


ft 


Si 


fti 


ft 


Si 






H^ 


Ph 


pq 


H^ 


« 


pq 


(T* M 


Ph 


P5 


H^ 


p^ 


pq 


H^ 


p^ 


pq 




« 


ffl 


6060 


1200 


3955 


315 


1.91 


4152 


331 


2.33 


4470 


356 


2.83 


4950 


394 


3.31 


5230 


417 


3.86 


5750 


458 


5.00 


6565 


130C 


4050 


322 


2.08 


4380 


349 


2.54 


4550 


363 


3.03 


5024 


400 


3.56 


5295 


421 


4.12 


5820 


464 


5.25 


7070 


140C 


4143 


329 


2.28 


4465 


356 


2.77 


4700 


375 


3.29 


5105 


407 


3.83 


5350 


426 


4.42 


5900 


470 


5.58 


7575 


1500 


4250 


338 


2.51 


4570 


364 


3.02 


4850 


386 


3.54 


5180 


413 


4.10 


5450 


434 


4.68 


5950 


475 


5.93 


8080 


160r 


4325 


345 


2.75 


4652 


371 


3.29 


4950 


395 


3.83 


5245 


418 


4.39 


5550 


442 


5.02 


6025 


480 


6.27 


8585 


1700 


4437 


353 


3.01 


475C 


378 


3.61 


5040 


402 


4.15 


5330 


424 


4.74 


5625 


448 


5.35 


6100 


486 


6.63 


9090 


1800 


4527 


361 


3.29 


4846 


386 


3.89 


5110 


407 


4.46 


5410 


431 


5.10 


5700 


455 


5.73 


6195 


493 


7.05 


9595 


1900 


4613 


368 


3.59 


4945 


394 


4.19 


5230 


417 


4.81 


5520 


440 


5.48 


5780 


460 


6.13 


6265 


499 


7.47 


10100 


20or 


4743 


377 


3.91 


5075 


404 


4.55 


5325 


424 


5.19 


5620 


448 


5.88 


5860 


467 


6.57 


6365 


507 


7.92 


10605 


210c 


4850 


386 


4.25 


5145 


410 


4.92 


5440 


433 


5.60 


5724 


456 


6.32 


5955 


475 


7.00 


6475 


516 


8.45 


11110 


220c 


497C 


396 


4.64 


5256 


419 


5.31 


5550 


443 


6.02 


5790 


461 


6.74 


6050 


482 


7.45 


6550 


522 


8.96 


11615 


230C 


5090 


405 


5.36 


537t 


427 


5.75 


5630 


448 


6.45 


5900 


470 


7.22 


6150 


490 


7.95 


6610 


527 


9.52 


12120 


240f 


521(1 


416 


5.48 


548(1 


437 


6.20 


5750 


458 


6.92 


6025 


48(1 


7.72 


6270 


50C 


8.48 


670(1 


534 


10.10 


12625 


2500 


5340 


425 


5.96 


5610 


447 


6.66 


5850 


466 


7.45 


6100 


486 


8.23 


6343 


505 


9.06 


6800 


542 


10.68 


131.30 


2600 


5485 


437 


6.44 


o74f 


457 


7.22 


5980 


477 


7.98 


620C 


494 


8.78 


6460 


515 


9.67 


688C 


548 


11.30 


14140 


2800 


.571C 


455 


7.60 


596f 


475 


8.33 


6230 


497 


9.19 


646C 


515 


10.05 


6650 


530 


10.90 


709C 


564 


12.68 


15150 


300f 


597C 


476 


8.73 


620C 


494 


9.60 


646(1 


515 


10.53 


6675 


532 


11.38 


6900 


55C 


12.33 


7295 


581 


14.16 


16160 


320C 


623C 


497 


10.05 


6475 


517 


11.00 


673C 


537 


11.97 


6920 


551 


12.88 


7135 


568 


13.86 


7530 


600 


15.73 


17179 


340f 


658C 


524 


11.62 


674(1 


537 


12.62 


696(1 


555 


13.60 


715(1 


57(1 


14.60 


7355 


587 


15.55 


775( 


618 


17.58 


18180 


3600 


6815 


543 


13.23 


7000 


559 


14.30 


7200 


574 


15.40 


7440 


59.': 


16.38 


7600 


605 


17.48 


8020 


639 


19.50 


19190 


3800 


7105 


565 


15.10 


7350 


586 


16.27 


7475 


596 


17.30 


7660 


611 


18.38 


7840 


624 


19.44 


8220 


655 


21.73 



280 



HEATING AND VENTILATION 



CAPACITY TABLE 
Table VII. — No. 90 Single Inlet Steel Plate Fan- 



-Type S 







S 


P. 


H" 


S. P. H" 


s. P. y2" 


s. P. ys" 


S. P. ^ 


i" 


S. P. J^" 


Vol- 
ume 


11 


























d 

.a 




d 


d 




d 


d 


T3 


a 

d 


d 

.£3 


73 

a$ 


a 

d 


d 


a1 


a 

d 


d 






H^ 


P^ 


« 


H^ 


rt 


« 


H^ 


rt 


ffl 


H^ 


rt 


m 


H to 


rt 


m 


H^ 


rt 


m 


6450 


1000 


2365 


167 


.625 


2690 


190 


.835 


2940 


208 


1.05 


3175 


224 


1.27 


3400 


240 


1.49 


3610 


255 1.75 


7095 


1100 


2490 


176 


.735 


278C 


196 


.965 


3040 


215 


1.19 


3267 


231 


1.43 


348C 


246 


1.68 


3670 


259 1.93 
266 2.14 


7740 


1200 


2600 


184 


.876 


2925 


207 


1.11 


3125 


221 


1.35 


3360 


238 


1.61 


35751 253 


1.88 


3763 


8385 


i30f: 


2736 


193 


1.03 


3000 


212 


1.27 


3237 


2291 1.54 


3475 


245 


1.81 


3675, 259 


2.09 


3865 


273! 2.37 


9030 


140f 


2846 


201 


1.20 


3107 


220 


1.46 


3310 


234i 1.73 


357a 


25a 


2.03 


3750 265 


2.31 


3965 


280 2.61 


9675 


1500 


2987 


211 


1.40 


3226 


228 


1.68 


3460 


2441 1-97 


3650 


258 


2.26 


3860 


273 


2.57 


4060 


287i 2.89 


10320 


1600 


3130 


221 


1.61 


3350 


237 


1.91 


3565 


2521 2.21 


3765 


266 


2.52 


396C 


28(1 


2.84 


4160 


2941 3.17 


10965 


1700 


3270 


231 


1.85 


3475 


245 


2.17 


3680 


260[ 2.48 


3885 


275 


2.81 


4055 


287 


3.15 


4250 


300 3.49 


11610 


1800 


3410 


241 


2.15 


3607 


255 


2.45 


3810 


269' 2.79 


4010 


283 


3.12 


4180 


296 


3.54 


4350 


308 3.86 


12255 


1900 


3546 


251 


2.40 


3730 


264 


2.76 


3935 


278! 3.10 


4120 


291 


3.46 


4320 


305 


3.83 


4455 


315! 4.19 


12900 


2000 


3700 


262 


2.72 


386t 


273 


3.09 


4050 


286 


3.46 


4255 


301 


3.86 


4423 


313 


4.22 


458C 


324 4.62 


13545 


2100 


3850 


272 


3.06 


4000 


283 


3.47 


4210 


298 


3.82 


4350 


308 


4.25 


4535 


320 


4.64 


4680 


331^ 5.03 


14190 


2200 


1000 


283 


3.43 


1168 


295 


3.88 


4320 


305 


4.27 


4500 


318 


4.68 


1670 


330 


5.11 


4800 


340 5.52 


14835 


2300 








4323 


306 


4.30 


4450 


314 


4.69 


4628 


327 


5.13 


4770 


338 


5.59 


493C 


348i 6.02 


15480 


2400 








4460 


315 


4.64 


4620 


327 


5.21 


4740 


335 


5.65 


1920 


348 


6.22 


5045 


356 6.55 


16125 


2500 








4600 


325 


5.24 


4720 


334 


5.71 


4880 


347 


6.19 


50361 356 


6.64 


517C 


366 7.13 


16770 


2600 














4910 


348 


6.31 


5000 


354 


6.77 


5180 366 


7.28 


5325 


3761 7.74 


18060 


2800 














5180 


366 


7.47 


5280 


373 


8.05 


5435! 384 


8.53 


5510 


390 9.12 


19350 


3000 














5485 


387 


8.87 


5610 


397 


9.48 


5650 


400 


9.98 


5840 


41410.57 







S. P. 1" 


S. p. IM" 


S. 


P. m" 


S. P. m" 


S. P. 2" 


S. 


P. 2>^" 


Vol- 










































ume 




V. 


a 


d 


'S 


a 


d 


'S 


a 


d 


'^ 


a 


d 


'S 


a 


d 


V, 


a 


d 




ol 


aS 


d 


M 


2-s 


d 


,£i 


s-s 


d 


.£3 


s-s 


d 


rC 


S-^ 


d 


X 


aS 


d 


JS 






H& 


P^ 


w 


H^ 


tf 


m 


H& 


p4 


m 


H& 


tf 


m 




« 


pq 


H& 


tf 


« 


7740 


1200 


3955 


279 2.44 


4152 294 


2.98 


4470 


316 


3.61 


4950 


350 


4.23 


5230 


370 


4.93 


5750 


406 


6.38 


8385 


1300 


4050 


2861 2.65 


43801 309 


3.25 


4550 


322 


3.88 


5024 


353 


4.56 


5295 


374 


5.26 


5820 


411 


6.71 


9030 


1400 


4143 


293 2.92 


4465 316 


3.55 


4700 


i 332 


4.21 


5105 


361 


4.88 


5350 


378 


5.65 


5900 


417 


7.13 


9675 


1500 


4250 


300 3.21 


4570: 323 


3.86 


4850 


1 343 


4.53 


5180 


366 


5.24 


5450 


385 


5.98 


5950 


420 


7.57 


10320 


1600 


4325 


306 3.51 


1652i 329 


4.21 


4950 


350 


4.89 


5245 


370 


5.61 


5550 


392 


6.41 


6025 


427 


8.02 


10965 


1700 


4437 


313 3.84 


47501 336 


4.61 


5040 


356 


5.31 


5330 


377 


6.06 


5625 


398 


6.83 


6100 


431 


8.48 


11610 


1800 


4527 


320 4.20 


48461 342 


4.96 


5110 


362 


5.70 


5410 


383 


6.52 


5700 


403 


7.32 


6195 


438 


9.02 


12255 


1900 


4613 


327 4.58 


4945! 350 


5.35 


5230 


370 


6.15 


5520 


393 


7.00 


5780 


408 


7.82 


6265 


443 


9.55 


12900 


2000 


4743 


335 5.00 


50751 3591 5.81 
5145| 364 6.29 


5325 


377 


6.63 


5620 


398 


7.52 


5860 


415 


8.38 


6365 


450 


10.12 


13545 


2100 


4850 


343 5.43 


5440 


384 


7.15 


5724 


405 


8.07 


5955 


421 


8.94 


6476 


458 


10.78 


14190 


2200 


4970 


352 5.82 


5256' 372' 6.78 


5550 


393 


7.70 


5790 


409 


8.62 


6050 


428 


9.52 


6550 


463 


11.45 


14835 


2300 


5090 


360 6.61 


53701 3801 7.35 
5480! 3871 7.92 


5630 
5750 


398 


8.25 


5900 


417 


9.23 


6150 


435 


10.15 


6610 


467 


12.13 


15480 


2400 


5210 


369 7.01 


406 


8.85 


6025 


427 


9.87 


6270 


442 


10.84 


6700 


474 


12.88 


16125 


2500 


5340 


377' 7.62 


5610 3961 8.52 


5850 


413 


9.52 


6100 


432 


10.50 


6343 


449 


11.96 


6800 


480 


13.63 


16770 


2600 


5485 


388! 8.25 


5740i 405i 9.22 


5980 


424 


10.20 


6200 


438111.22 


6460 


456 


12.35 


6880 


487 


14.44 


18060 


2800 


5710 


404 9.72 


5960: 422 10.65 


6230 


441 


11.74 


6460 


457il2.83 


6650 


470 


13.73 


7090 


501 


16.20 


19350 


3000 


5970 


42211.15 


6200 438:i2.25 


6460 


457 


13.45 


6675 


472 14.55 


6900 


488 


15.73 


7295 


515 


18.05 


20640 


3200 


6230 


44112.83 


64751 45114. 05 


6730 
6960 


476 


15.30 


6920 


48916.44 


7135 


503 


17.70 


7530 


533 


20.10 


21930 


3409 


6580 


46514.85 


67401 477il6.10 


492 


17.35 


7150 


50518.65 


7355 


519 


19.86 


7750 


548 


22.45 


23220 


3600 


6815 


482 16.90 


7020' 497,18.25 


7200 


510 


19.65 


7440 


525 20.92 


7600 


538 


22.30 


S020 


567 


24.87 


24510 


3800 


7105 


50319.30 

t 


7350 520,20.75 


7475 


528 


22.13 


7660 


542I23.53 

1 


7840 


554 


24.85 


8220 


581 


27.75 



APPENDIX 



281 



Table VIII.- 



CAPACITY TABLE 

-No. 100 Single Inlet Steel Plate Fan- 



-Type S 







s 


.P. 


yi" 


S 


P. W 


s 


P. 


y2" 


S. P. M" 


s 


P. %" 


S. P. Vs" 


Vol- 
ume 




























a1 


6 
ft 




ft^ 


ft 


i, 


ft^ 


B 

ft 


ft 


ftl 


a 
ft 


ft 


ft?, 


B 
ft 


ft 

Xi 


a1 


a 

ft 


ft 






« 


ffl 


'C ft 


P5 


pq 




^ 


pq 


H& 


tf 


pq 


H& 


rt 


pq 


■^^ 


« 


pq 


82G0 


1000 


2366 


150 


.800 


2890 


.71 


1.07 


2940 


187 


1.34 


3175 


202 


1.62 


3400 


216 


1.92 


3610 


230 


2.24 


9086 


nof 


249(1 


158 


.942 


278(; 


177 


1.23 


304(J 


193 


1.53 


3267 


208 


1.84 


348(] 


221 


2.15 


367(1 


234 


2.47 


9912 


1200 


2600 


165 


1.12 


2925 


186 


1.43 


3125 


199 


1.73 


3360 


214 


2.06 


3575 


227 


2.40 


3763 


240 


2.74 


10738 


1300 


2736 


174 


1.32 


300C 


191 


1.64 


3237 


206 


1.97 


3475 


221 


2.37 


3675 


233 


2.67 


3865 


246 


3.03 


11564 


1400 


2846 


181 


1.53 


3107 


198 


1.87 


3310 


211 


2.21 


3573 


227 


2.59 


3750 


239 


2.96 


3965 


252 


3.35 


12390 


1500 


2987 


190 


1.79 


3226 


205 


2.14 


3460 


220 


2.52 


3650 


233 


2.90 


3860 


246 


3.28 


4060 


258 


3.69 


13216 


1600 


3130 


199 


2.06 


33.50 


213 


2.44 


3565 


227 


2.82 


3765 


240 


3.23 


3960 


252 


3.63 


4160 


265 


4.07 


14042 


1700 


3270 


208 


2.37 


3475 


222 


2.77 


3680 


234 


3.17 


3885 


247 


3.59 


4055 


258 


4.03 


4250 


27C 


4.47 


14868 


180C 


3410 


217 


2.75 


3607 


230 


3.14 


3810 


242 


3.57 


4010 


255 


3.99 


4180 


266 


4.53 


4350 


277 


4.95 


1569-1 


190C 


3546 


226 


3.07 


3730 


237 


3.54 


3935 


252 


3.97 


4120 


262 


4.43 


4320 


275 


4.90 


4455 


284 


5.37 


1652C 


200C 


3700 


235 


3.47 


3860 


245 


3.97 


4050 


258 


4.43 


4255 


269 


4.93 


4423 


282 


5.41 


4580 


292 


5.90 


17346 


2 IOC 


3850 


245 


3.92 


4000 


254 


4.43 


421(; 


268 


4.88 


4350 


277 


5.44 


4535 


289 


5.95 


4680 


298 


6.44 


18172 


2200 


4000 


254 


4.39 


4168 


265 


4.97 


4320 


275 


5.47 


4500 


286 


6.00 


4670 


297 


6.54 


4800 


306 


7.06 


18998 


2300 








4323 


275 


5.50 


4450 


283 


6.01 


4628 


294 


6.57 


4770 


303 


7.15 


4930 


314 


7.70 


19824 


2400 








4460 


284 


5.95 


4620 


294 


6.67 


47401 302 


7.23 


4920 


313 


7.82 


5045 


321 


8.38 


2065C 


250(; 








4600 


293 


6.70 


4720 


301 


7.32 


4880 310 


7.92 


5036 


320 


8.52 


517(1 


32^ 


9.13 


21476 


2600 














4910 


312 


9.08 


5000 318 


8.52 


5180 


329 


9.33 


5325 


339 


9.92 


2312S 


2800 














5180 


330 


9.57 


5280 338 


10.30 


5435 


346 


10.92 


5510 


351 


11.67 


24780 


3000 














5485 


349 


11.34 


5610 


357 


12.14 


5650 


359 


12.77 


5840 


371 


13.53 







S. P. 


1" 


S. 


P. IK" ■ 


S. 


P. IK" 


S. P. IH" 


S. P 2" 


S. 


P. 2K" 


Vol- 
ume 


«:> 






















JH 


'^ 


a 


ft 


"S 


a 


ft 


Ti 


a 


ft 




a 


ft 


T3 


a 


ft 


'^ 


a 


ft 




OS 


ft![, 


ft 


r£i 


ftff, 


ft 


M 


ftfl* 


ft 


Xi 


ft 


Xi 


ftfl'', 


ft 


Xi 


ftfl*, 


ft 


Xi 




H& 


P^ 


PQ 


^g- 


(A 


pq 




rt 


pq 


H& 


tf 


pq 


H& 


rt 


pq 




^ 


« 


9912 


1200 


3955 


251 


3.12 


4152 


264 


3.82 


4470 


285 


4.62 


4950 


315 


5.42 


5230 


333 


6.36 


5750 


366 


8.17 


10738 


1300 


mr, 


258 


3.41) 


438(: 


278 


4.16 


455(1 


290 


4.96 


5024 


320 


5.83 


5295 


337 


6.72 


5820 


370 


8.60 


11564 


1400 


4143 


263 


3.74 


4465 


285 


4.54 


4700 


299 


5.38 


5105 


325 


6.25 


5350 


340 


7.22 


5900 


375 


9.13 


12390 


1500 


42.5r 


'27(1 


4.11 


457(; 


291 


4.93 


4850 


308 


5.80 


5180 


329 


6.72 


5450 


347 


7.67 


5950 


379 


9.72 


13216 


1600 


4325 


275 


4.50 


4652 


297 


5.38 


4950 


315 


6.27 


5245 


334 


7.18 


5550! 353 


8.20 


6025 


383 


10.26 


14042 


1700 


4437 


282 


4.92 


475C 


302 


5.90 


5040 


321 


6.79 


5330 


339 


7.75 


5625' 358 


8.76 


6100 


388 


10.85 


14868 


1800 


4527 


288 


5.38 


4846 


308 


6.36 


5110 


325 


7.29 


5410 


344! 8-36 


57001 363 


9.37 


6195 


394 


11.55 


15694 


1900 


46131 294 


5.86 


4945 


314 


6.85 


5230 


333 


7.87 


5520 


351; 8.97 


5780; 368 


10.02 


6265 


398!l2.22 


16520 


2000 


4743 301 


6.41 


5075 


323 


7.44 


5325 


339 


8.50 


5620 


357! 9.63 


5860; 373 


10.73 


6365 


405 


12.97 


17346 


2100 


4850 i 308 


6.95 


5145 


328 


8.05 


5440 


346 


9.17 


5724 


364,10.32 


5955; 379ill.44 


6475 


412 


13.80 


18172 


2200 


4970! 316 


7.58 


5256 


334 


8.68 


5550 


354 


9.85 


5790; 36811.03 


6050! 385;12.18 


6550 


417 


14.65 


18998 


2300 


50901 324 


8.60 


5370 


342 


9.42 


5630 


358 


10.55 


5900 


375111.82 


6150! 39l'l3.00 


6610 


421 


15.54 


19824 


2400 


5210; 332 


8.97 


548(i 


349 


10.15 


575(1 


366 


11.32 


3025 


38312.64 


6270 399,13.86 


6700 


426 


16.51 


20650 


2500 


5340 340 


9.75 


5610 


357 


10.90 


5850 


372 


12.18 


6100 


38813.46 


6343! 403;i4.80 


6800 


43217.48 


21476 


2600 


54851 349 


10.55 


5740 


366 


11.80 


5980 


381 


13.06 


62001 39414.37 


6460i 411 15.80 


6880 


438;18.50 


23128 


2800 


5710! 364 


12.43 


5960 


379 


13.62 


6230 


396 


15.03 


6460' 41116.42 


6650 42317.85 


7090 


45120.73 


24780 


3000 


59701 380 


14.28 


6200 


395 


15.68 


6460 


411 


17.20 


6675! 42518.63 


6900' 439I2O.I5 


7295 


464 23.15 


26432 


3200 


6230i 396 


16.43 


6475 


412 


18.00 


6730 


428 


19.60 


6920; 44121.07 


7135! 448i22.67 


7530 


478125.73 


28084 


3400 


6580 418 


19. .00 


6740 


429 


20.60 


6960 


443 


22.25 


7150i 455 23.88 


7355' 469125. 40 


7750 


49328.70 


29736 


3600 


6815i 433 


21.65 


702(1 


447 


23.35 


7200 


458 


25.13 


7440 47326.75 


7600! 484!28.60 


8020 


51131.90 


31388 


3800 


7105 452 


24.70 


7350 


468 


26.60 


7475 


476 


28.30 


7660 488,30.10 


7840| 499,31.80 


8220 


523 35.55 



282 



HEATING AND VENTILATION 



CAPACITY TABLE 

Table IX. — No. 110 Single Inlet Steel Plate Fan — Type S 







S 


P. 


H" 


S 


P. 


ys" 


S 


P. H" 


s 


P. 


ys" 


S 


P.H" 


S 


P. H" 


Vol- 
ume 


d > 

O 
































al 




ft 


ftl 


B 

ft 


a 


ftl 


ft 


ft 


ftl 


i 


ft 

J3 


ftl 


ft 


ft 


ftfl) 


a 

ft 


ft 






H& 


« 


« 


H& 


« 


pq 


H^ 


« 


pq 


Hg- 


Pi 


pq 


H& 


tf 


pq 


Hg* 


rt 


pq 


9760 


1000 


2366 


137 


.945 


2690 


156 


1.26 


2940 


170 


1.58 


3175 


184 


1.92 


3400 


197 


2.26 


3610 


209 


2.65 


10736 


1100 


2490 


144 


1.11 


2780 


161 


1.46 


3040 


176 


1.81 


3267 


190 


2.17 


3480 


202 


2.53 


3670 


212 


2.93 


11712 


1200 


2600 


151 


1.32 


2925 


169 


1.69 


3125 


181 


2.05 


3360 


195 


2.44 


3575 


207 


2.84 


3763 


218i 3.24 


12688 


1300 


2736 


157 


1.56 


3000 


174 


1.93 


3237 


187 


2.32 


3475 


201 


2.74 


3675 


213 


3.16 


3865 


224 3.58 


13664 


1400 


2846 


165 


1.81 


3107 


180 


2.21 


3310 


192 


2.61 


3573 


207 


3.06 


3750 


217 


3.50 


3965 


230 3.96 


14640 


1500 


2987 


173 


2.12 


3226 


187 


2.54 


3460 


200 


2.97 


3650 


211 


3.43 


3860 


224 


3.88 


4060 


235 4.37 


15616 


1600 


3130 


183 


2.44 


3350 


194 


2.89 


3565 


207 


3.34 


3765 


218 


3.81 


3960 


229 


4.29 


4160 


241 4.80 


16592 


1700 


3270 


189 


2.79 


3475 


201 


3.27 


3680 


213 


3.74 


3885 


225 


4.24 


4055 


235 


4.76 


4250 


246i 5.28 


17568 


1800 


3410 


197 


3.25 


3607 


209 


3.71 


3810 


221 


4.22 


4010 


232 


4.72 


4180 


242 


5.36 


4350 


252 5.84 


18544 


1900 


3546 


206 


3.63 


3730 


216 


4.18 


3935 


228 


4.68 


4120 


239 


5.23 


4320 


250 


5.79 


4455 


258| 6.34 


19520 


2000 


3700 


214 


4.11 


3860 


224 


4.68 


4050 


235 


5.22 


4255 


245 


5.82 


4423 


257 


6.39 


4580 


265 6.97 


20496 


2100 


385(] 


223 


4.63 


4000 


232 


5.24 


^21(1 


244 


5.77 


4350 


252 


6.42 


4535 


262 


7.02 


4680 


2711 7.61 


21472 


2200 


4000 


232 


5.18 


4168 


242 


5.87 


4320 


251 


6.46 


4500 


261 


7.08 


4670 


271 


7.72 


4800! 278! 8.34 


22448 


2300 








4323 


251 


6.50 


4450 


258 


7.10 


4628 


268 


7.76 


4770 


277 


8.45 


4930 


286, 9.12 


23424 


2400 








4460 


258 


7.02 


i620 


268 


7.88 


4740 


275 


8.55 


4920 


285 


9.24 


5045 


292! 9.92 


2440( 


2500 








4600 


266 


7.93 


4720 


273 


8.63 


4880 


283 


9.37 


5036 


292 


10.05 


5170 


30010.77 


25376 


2600 














4910 


284 


9.55 


5000 


290 


10.25 


5180 


300 


11.00 


5325 


30811.72 


27328 


2800 














5180 


300 


11.3 


5280 


306 


12.17 


5435 


315 


12.88 


5510 


31913.80 


29280 


3000 














5485 


317 


13.4 


5610 


325 


14.34 


5650 


327 


15.08 


5840 


33816.00 







S. P. 1" 


S. 


P. IK" 


S. P. ni" 


S. 


P. IH" 


S. P. 2" 


S. P. 2H" 


Vol- 
ume 


ST) 


















'S 


a 


ft 


'S 


a 


ft 


XI 


a 


ft 


7 


a 


ft 


^1^ 


ft 


■^ 


a 


0, 




u > 


ftn"". 


ft 


.£3 


a^, 


ft 


.c 


fta") 


ft 


rC 


fta") 


ft 


ra 


ft^ ft 


ji 


ftii) 


ft 


rC 






H& 


« 


pq 


Hg' 


tf 


pq 


H^ 


rt 1 pq 


H^ 


P5 


pq 


h^Ipj 


n 


H& 


pr? 


pq 


11712 


1200 


3955 


229 


3.69 


41.52 


241 


4.52 


4470 


259 


5.47 


4950 


287 


6.40 


5230 


303 


7.45 


5750 


333 


9.64 


12688 


1300 


4050 


235 


4.02 


4380 


254 


4.92 


4550 


264 


5.87 


.5024 


291 


6.88 


5295 


306 


7.95 


5820 


337 


10.15 


13664 


1400 


4143 


240 


4.42 


4465 


259 


5.37 


4700 


272 


6.36 


5105 


296 


7.38 


5350 


310 


8.53 


5900 


342 


10.78 


14640 


1500 


4250 


246 


4.85 


4570 


265 


5.83 


4850 


281 


6.85 


5180 


300 


7.93 


5450 


316 


9.06 


5950 


345 


11.46 


1.5616 


1600 


4325 


250 


5.32 


4652 


270 


6.37 


4950 


287 


7.40 


5245 


303 


8.50 


5550 


322 


9.69 


6025 


349 


12.13 


16592 


1700 


4437 


257 


5.81 


4750 


275 


6.97 


5040 


292 


8.02 


5330 


309 


9.17 


5625 


326 


10.34 


6100 


353 


12.83 


17568 


1800 


4527 


262 


6.35 


4846 


280 


7.50 


5110 


296 


8.62 


5410 


313 


9.86 


5700 


330!11.07 


5195 


358 


13.65 


18544 


1900 


4613 


267 


6.92 


4945 


286 


8.10 


5230 


303 


9.30 


5520 


320 


10.58 


5780 


33511.84 


3265 


363 


14.44 


19520 


2000 


4743 


274 


7.57 


.5075 


294 


8.80 


5325 


309 


10.03 


5620 


325 


11.37 


5860 


340|12.68 


6365 


369 


15.32 


20496 


2100 


4850 


281 


8.22 


5145 


298 


9.52 


5440 


315 


10.83 


5724 


332 


12.20 


5955 


345!l3.52 


6475 


375 


16.30 


21472 


2200 


4970 


288 


8.96 


5256 


305 


10.24 


5550 


322 


11.63 


5790 


335 


13.02 


6050 


350114.40 


6550 


379 


17.30 


22448 


2300 


5090 


295 


10.15 


5370 


311 


11.11 


5630 


326 


12.48 


5900 


342 


13.96 


6150 


35615.37 


6610 


383 


18.37 


23424 


2400 


5210 


302110.62 


5480 


312 


11.99 


5750 


333 


13.39 


6025 


349 


14.93 


6270 


363(16.39 


6700 


388 


19.54 


24400 


2500 


5340 


309 


11.52 


5610 


325 


12.88 


5850 


339 


14.38 


6100 


353 


15.90 


6343 


36717.50 


6800 


394 


20.65 


25376 


?600 


5485 


318 


12.47 


5740 


332 


13.96 


5980 


346 


15.43 


6200 


359 


16.97 


6460 


375118.70 


6880 


399 


21.86 


27328 


?800 


5710 


331 


14.68 


5960 


345 


16.10 


6230 


361 


17.75 


6460 


375 


19.43 


6650 


385:21.08 


709C 


405 


24.50 


29280 


3000 


5970 


346 


16.87 


6200 


359 


18.55 


6460 


374 


20.39 


6675 


387 


22.00 


6900 


400 23.80 


7295 


423 


27.33 


31232 


3200 


6230 


361 


19.43 


6475 


375 


21.30 


6730 


390 


23.10 


6920 


401 


24.90 


7135 


413 


26.75 


7530 


437 


30.46 


33184 


3400 


6580 


381 


22.45 


6740 




24.35 


6960 


403 


26.55 


7150 


414 


28.20 


7355 


427 


30.10 


7750 


449 


33.95 


35136 


3600 


6815 


395j25.55 


7020 


407 


27.60 


7200 


417 


29.70 


7440 


431 


31.60 


7600 


440 


33.75 


8020 


465 


37.70 


37088 


3800 


7105 


412 29.15 


7350 


426 


31.47 


7475 


433 


33.35 


7660 


444 


35.55 


7840 


454 


37.55 


8220 


476 


42.00 



APPENDIX 



283 



CAPACITY TABLE 

Table X. — No. 120 Single Inlet Steel Plate Fan — Type S 







S. P. K" 


S. P. 


Vs" 


S. P. H" 


S. P. 


ys" 


s. P. H" 


S 


P. Vs" 


Vol- 
ume 






















ll 


a1 


a 
ft 


a 


ftl 


a 

d 


ft 


ftl 


a 
ft 


a 


ftl 


a 
ft 


ft 


ftS 


a 
ft 


ft 


a1 


a 
ft 


ft 






Eh'& 


rt 


« 


Hg- 


« 


« 


H& 


tf 


m 


H^ 


p^ 


ffl 


H (C 


p^ 


pq 


N ^ 


« 


m 


11950 


1000 


2366 


125 


1.156 


2690 


143 


1.54 


2940 


156 


1.44 


3175 


168 


2.35 


3400 180 


2.77 


3610 


191 


3.24 


13145 


1100 


2490 


132 


1.36 


2780 


147 


1.79 


3040 


161 


2.21 


3267 


173 


2.66 


3480 185 


3.11 


3670 


195 


3.59 


14340 


1200 


2600 


138 


1.60 


2925 


155 


2.07 


3125 


166 


2.51 


3360 


178 


2.99 


3575] 189 


3.48 


3763 


200 


3.97 


15535 


1300 


2736 


145 


1.91 


3000 


159 


2.36 


3237 


172 


2.85 


3475 


184 


3.36 


3675, 195 


3.87 


3865 


205 


4.39 


16730 


1400 


2846 


151 


2.23 


3107 


165 


2.71 


3310 


176 


3.20 


3573 


189 


3.75 


3750 


199 


4.29 


3965 


210 


4.85 


17925 


1500 


2987 


158 


2.60 


3226 


171 


3.11 


3460 


184 


3.64 


3650 


194 


4.20 


3860 


205 


4.76 


4060 


215 


5.35 


19120 


160( 


3130 


166 


2.99 


3350 


178 


3.54 


3565 


m^ 


4.08 


3765 


20(; 


4.67 


3960 


210 


5.26 


4160 


220 


5.87 


20315 


1700 


3270 


173 


3.42 


3475 


184 


4.02 


3680 


195 


4.61 


3885 


206 


5.19 


4055 


215 


5.88 


4250 


226 


6.48 


21510 


1800 


3410 


181 


3.99 


3607 


191 


4.54 


3810 


202 


5.17 


4010 


213 


5.79 


4180 


222 


6.56 


43.50 


231 


7.16 


22705 


190r 


3546 


188 


4.45 


3730 


198 


5.12 


3935 


209 


5.74 


412C 


219 


6.42 


432C 


22fl 


7.10 


4455 


236 


7.77 


23900 


20or 


3700 


196 


5.04 


3860 


205 


5.74 


405(] 


215 


6.40 


4255 


226 


7.14 


4423 


235 


7.83 


458C 


243 


8.54 


25095 


210C 


3850 


204 


5.68 


4000 


212 


6.42 


4210 


223 


7.08 


4350 


231 


7.87 


4535 


241 


8.61 


468C 


248 


9.33 


2629C 


220C 


4000 


212 


6.36 


4168 


221 


7.19 


4320 


229 


7.92 


450C 


239 


8.68 


467C 


248 


9.47 


4800 


254 


10.22 


27485 


2300 








4323 


230 


8.08 


4450 


236 


8.70 


4628 


245 


9.51 


4770 


253 


10.35 


4930 


262 


11.15 


2868C 


2400 








4460 


237 


8.62 


4620 


245 


9.65 


474C 


251 


10.45 


492C 


261 


11.33 


5045 


268 


12.14 


39375 


250C 








4600 


244 


9.70 


4720 


251 


10.58 


4880 


259 


11.48 


5036 


267 


12.32 


5170 


275 


13.20 


31070 


2600 














4910 


261 


11.70 


500C 


265 


12.55 


5180 


275 


13.48 


5.325 


282 


14.35 


33460 


2800 














5180 


275 


13.87 


5280 


280 


14.92 


5435 


288 


15.80 


5510 


292 


16.88 


35850 


3000 














5485 


291 


16.40 


5610 


298 


17.88 


5650 


300 


18.48 


5840 


310 


19.60 







S. P. 1" 


S. 


P. IM" 


•s. 


P. IVi" 


S. 


P. IH" 


S. P. 2" 


S. P. 2H" 


Vol- 


a> 








































ume 


^1 


ftl 


a 


ft 


afi 


a 


d 


'? 


a 


d 


^ 


a 


d 


ftS 


a 


d 


t3 
ft?> 


a 


d 




■o' 


ft 


r^i 


ft 


.X3 


ftfl-) 


ft 


^ 


Q,h 


ft 


^ 


ft 


^ 


ft 


M 






H& 


rt 


pq 


H& 


p^ 


pq 


H& 


« 


m 


H& 


p^ 


pq 




rt 


pq 


H °" 


P5 


pq 


14340 


1200 


3955 209 


4.52 


4152 


220 


5.52 


4470 


237 


6.69 


4950 


262 


7.83 


5230 


279 


9.12 


5750 


305 


11.73 


15535 


1300 


4050 215 


4.92 


4380 


232 


6.02 


4550 


242 


7.18 


5024 


267 


8.43 


5295 


281 


9.75 


5820 


309 


12.4 


16730 


1400 


4143 


220 


5.40 


4465 


237 


6.57 


4700 


249 


7.80 


5105 


271 


9.04 


5350 


284 


10.44 


5900 


313 


13.2 


17925 


1500 


4250 


226 


5.95 


4570 


243 


7.15 


4850 


257 


8.40 


5180 


275 


9.73 


5450 


289 


11.10 


5950 


316 


14.0 


19120 


1600 


3325 


229 


6.50 


4652 


247 


7.80 


4950 


263 


9.08 


5245 


278 


10.40 


5550 


294 


11.87 


6025 


320 


14.8 


20315 


1700 


4437 


235 


7.12 


4750 


252 


8.55 


5040 


268 


9.84 


5330 


283 


11.22 


5625 


298 


12.1 


6100 


324 


15.7 


21510 


1800 


4527 


240 


7.78 


4846 


257 


9.20 


5110 


271 


10.56 


5410 


287 


12.10 


5700 


302 


13.6 


6195 


328 


16.7 


22705 


1900 


4613 


245 


8.48 


4945 


262 


9.92 


5230 


277 


11.33 


5520 


293 


12.9 


5780 


307 


14.5 


6266 


333 


17.7 


23900 


2000 


4743 


251 


9.27 


5075 


269 


10.77 


5325 


283 


12.3 


5620 


298 


13.9 


5860 


311 


15.5 


6365 


338 


18.7 


25095 


2100 


4850 


257 


10.07 


5145 


273 


11.67 


5440 


289 


13.2 


5724 


304 


14.9 


5955 


316 


16.5 


6475 


344 


20.0 


26290 


2200 


4970 


264 


10.97 


5256 


279 


12.56 


5550 


294 


14.2 


5790 


307 


15.9 


6050 


321 


17.6 


6550 


348 


21.2 


27485 


230( 


5090 


270112.45 


53 7(: 


285 


13.60 


563(1 


299 


15.3 


5900 


313 


17.1 


6150 


326 


18.8 


6610 


351 


22.5 


28680 


2400 


5210i 276112.98 


5480 


292 


14.70 


5750 


305 


16.4 


6025 


320 


18.3 


6270 


333 


20.1 


6700 


356 


23.9 


29875 


2500 


5340 


283114.12 


.5610 


298 


15.78 


5850 


310 


17.6 


6100 


324 


19.5 


6343 


336 


21.5 


6800 


361 


25.3 


31070 


260C 


5485 


29115.27 


5740 


304 


17.10 


5980 


317 


18.9 


6200 


329 


20.8 


6460 


343 


22.9 


6880 


365 


26.7 


33460 


2800 


5710 


303!l8.00 


5960 


316 


19.73 


6230 


331 


21.7 


6460 


343 


23.8 


6650 


353 


25.8 


7090 


376 


30.0 


35850 


300C 


5970 


317i20.68 


6200 


329 


22.70 


6460 


343 


24.9 


6675 


354 


26.9 


6900 


366 


29.2 


7295 


387 


33.5 


38240 


3200 


6230' 3.30123.80 


6475 


344 


26.10 


6730 


357 


28.3 


6920 


367 


30.5 


7135 


378 


32.8 


7530 


399 


37.2 


40630 


3400 


6580i 349:27.50 


6740 


357 


29.85 


6960 


320 


32.1 


7150 


379 


34.6 


7355 


391 


36.8 


7750 


411 


41.7 


43020 


360C 


6815 362131.30 


7000 


372 


33.80 


7200 


382 


36.4 


7440 


394 


38.7 


7600 


404 


41.4 


8020 


426 


46.2 


45410 


3800 


7105 377'35.80 


7350 


390 


38.50 


7475 


397 


41.0 


7660 


407 


43.6 


7840 


417 


46.0 


8220 


436 


51.4 



284 



HEATING AND VENTILATION 



Table XI. 



CAPACITY TABLE 

-No. 130 Single Inlet Steel Plate Fan — Type S 







S 


. P. 


Vi" 


S 


p. ?«" 


S 


p-y2" 


S 


P. H" 


S 


P.H" 


S. P. w 


Vol- 
ume 




























T5 


a 


a 


T) 


s 


a 


-c 


Q 


a 


a?> 


e 


a 


a1 


S 


a 


a1 


S 


a 




a 


rC 


afl^ 


a 


-C 


aS 


a 


-£3 


a 


.c 


a 


ji 


a 


ji 






H& 


« 


PQ 


H& 


Pi 


pq 


H& 


« 


pq 


H& 


tf 


PQ 


H& 


P^ 


« 


H& 


!A 


pq 


14050 


1000 


2366 


116 


1.360 


2690 


132 


1.820 


2940 


144 


2.280 


3175 


156 


2.765 


3400 


166 


3.262 3610177 


3.810 


1545.5 


HOC 


2490 


122 


1.602 


2780 


136 


2.101 


3040 


149 


2.607 


3267 


160 


3.128 


348C 


171 


3.65J 


3670180 


4.218 


16860 


i20(: 


2600 


127 


1.909 


2925 


143 


2.433 


3125 


153 


2.952 


3360 


165 


3.516 


3575 


175 


4.091 


3763184 


4.668 


18265 


i30(: 


2736 


134 


2.250 


3060 


147 


2.790 


3237 


1.57 


3.351 


3475 


170 


3.95C 


3675 


180 


4.555 


38651189 


5.162 


19670 


i40(; 


2846 


139 


2.62C 


3107 


152 


3.190 


3310 


162 


3.771 


3573 


175 


4.414 


375C 


184 


5.0.50 


3965)194 


5.710 


21075 


1500 


2987 


146 


3.060 


3226 


158 


3.660 


3460 


170! 4.290 


3650 


179 


4.937 


3860 


189 


5.595 


40601199 


6.290 


22480 


160C 


3130 


154 


3.515 


3350 


164 


4.168 


3565 


175 


4.807 


3765 


185 


5.500 


3960 


193 


6.190 


41601204 


6.918 


23885 


170C 


3270 


160 


4.027 


3475 


170 


4.717 


3680 


180 


5.408 


3885 


190 


6.102 


4055 


197 


6.868 


4250208 


7.620 


25290 


180C 


3410 


167 


4.690 


3607 


177 


5.. 345 


3810 


187 


6.078 


4010 


196 


6.800 


418C 


205 


7.715 


4350213 


8.423 


20695 


1900 


3546 


174 


5.23C 


3730 


183 


6.02C 


3935 


193 


6.752 


4120 


202 


7.5.50 


4320 


212 


8.350 


44551218 


9.147 


28100 


2000 


3700 


181 


5.9.35 


3860 


189 6.250 


4050 


198 


7.540 


4255 


209 


8.400 


4423 


217 


9.210 


4580225 


10.04 


29505 


210C 


3850 


189 


6.678 


4000 


196 


7.550 


4210 


206 


8.320 


4350 


213 


9.253 


4535 


222 


10.120 


46801229110.97 


30910 


220C 


4000 


196 


7.475 


4168 


204 


8.452 


4320 


212 


9.300 


4500 


221 


10.20 


4670 


229 


11.120 


4800123512.02 


32315 


2300 








4323 


212 


9.230 


4450 


218 


10.23 


4628 


227 


11.18 


4770 


234 


12.17C 


49302421 13. 12 


33720 


2400 








4460 


219 


10.130 


4620 


226 


11.34 


4740 


232 


12.30 


4920 


241 


13.30 


5045 247114.26 


35125 


2500 








4600 


226 


11.40 


4720 


231 


12.43 


4880 


239 


13.48 


5036 


247 


14.48 


517025315.49 


36530 


2600 














4910 


241 


13.75 


5000 


245 


14.76 


5180 


254 


15.85 


532526116.87 


39340 


2800 














5180 


254 


16.29 


5280 


259 


17.53 


5435 


266 


18.60 


5410270(19.87 


42150 


3000 














5485 


269 


19.30 


5610 


275 


20.66 


5650 


277 


21.74 


5840 286:23.06 







S. P. 1" 


S. 


P. IK" 


S. P. IH" 


S. P. IH" 


S. P. 2" 


S. P. 2H" 


Vol- 
ume 


3-^ 
















-d 


a 




-c 


a 


a 


"S 


a 


a 


V. 


a 




Ti 


a 




-d 


a 






O > 


a^. 


a 


rG 


am 


a 


.£i 


ao^, 


a 


rG 


aH^. 


a 


43 


aH^) 


a 


^ 


a^. 


a 


JS 






H& 


« 


pq 


iH a 


rt 


pq 


H& 


rt 


PQ 




tf 


pq 


H& 


« 


PQ 


H& 


tf 


PQ 


16860 


1200 


39.55 


194 


5.303 


4152 


204 


6.501 


4470 


219 


7.875 


4950 


243 


9.32 


1 1 
.5230: 256110.73 


5750 


1 
28213.91 


18265 


1300 


4050 


198 


5.79C 


4380 


215 


7.085 


4550 


223 


8.351 


5024 


246 


9.93 


5295 25911.46 


.5820! 28514.63 


19670 


1400 


4143 


203 


6.355 


4465 


219 


7.337 


4700 


231 


9.160 


5105 


250!10.63 


5350' 26212.28 


5900 28915.53 
5950 291116.50 


21075 


1500 


4250 


208 


7.000 


457C 


224 


8.40C 


4850 


238 


9.87C 


5180 


254111.43 


5450i 26713.05 


22480 


1600 


4325 


212 


7.650 


4652 


229 


9.17C 


4950 


243 


10.67 


5245 


257il2.23 


5550, 27213.45 


60251 29517.49 


238.55 


1700 


4437 


217 


8.375 


4750 


233 


10.04 


5040 


247 


11.56 


5330 


26213.20 


.5625! 27614.90 


6100! 29918.48 


25290 


1800 


4.527 


222 


9.150 


4846 


238 


10.80 


5110 


251 


12.41 


5410 


265|14.25 


5700, 27915.94 


6195 


303119.65 


26695 


1900 


4613 


226 


9.98C 


4945 


243 


11.67 


5230 


256 


13.38 


5520 


27015.27 


5780 28317.05 


6265 


.307120.83 


28100 


2000 


4743 


232 


10.90 


5075 


249 


12.67 


5325 


261 


14.46 


5620 


275 


16.40 


5860: 28719.27 


6365 


312 


22.10 


29505 


:^100 


48.50 


238 


11.83 


5145 


252 


13.70 


.5440 


267 


15.59 


5724 


280 


17.88 


5955 29219.50 


6425 


317 


23.50 


30910 


2200 


4970 


243 


12.90 


5256 


257 


14.78 


5550 


272 


16.77 


5790! 284 


18.78 


6050- 296 20.73 


6550 


321 


24.94 


32315 


2300 


5090 


249 


14.63 


5370 


263 


16.00 


5630 


276 


17.99 


5900 


289 


20.10 


6150! 30122.13 


6610 


324 


26.46 


33720 


2400 


.5210 


255 


15.27 


5480 


269 


17.27 


5750 


282 


19.29 


6025 


295 21.50 


6270 30723.60 


6700 


329 28.10 


35125 


2,500 


534C 


262 


16.59 


5610 


275 


18.55 


5850 


287120.73 


6100 


299|22.90 


63431 31i;25.23 


6800 


333 29.73 


36530 


2600 


.5485 


269 


17.96 


5740 


281 


20.12 


5980 


293122.24 


6200 


304 24.38 


6460 31626.90 


6880 


33931.50 


39340 


2800 


5710 


280 


21.14 


5960 


292 


23.20 


6230 


305 25.60 


6460 


317128. 00 


6650 326 30.35 


7090 


342 35.30 


42150 


3000 


5970 


292 


24.32 


6200 


303 


26.72 


6460 


31729.30 


6675 


327 31.70 


6900 338 34.30 


7295 


35739.40 


44960 


3200 


6230 


305 


28.00 


6475 


317 


30.63 


673C 


330|33.32 


6920 


339i35.90 


7135 349.38.60 


7593 369:43.80 


47770 


3400 


6580 


322 


32.35 


6740 


330 


35.08 


6960 


34137.80 


7150 


35140.70 


7355 36143.30 


7750i 38049.00 


50580 


3600 


6815 


335 


36.82 


7020 


344 


39.80 


7200 


353 


42.80 


7440 


36545.60 


7600: 373 48.70 


8020 395 54.30 


53390 


3800 


7105 


349 


42.02 


7350 


360 


45.37 


7475 


367 


48.20 


7660 


375 51.20 


7840 384 54.20 


8220 403j60.50 



■ 



APPENDIX 



285 



Table XII. 



CAPACITY TABLE 

-No. 140 Single Inlet Steel Plate Fan — Type S 







s. p. 


J^" 


S 


P. rs" 


S 


P. K" 


S 


P. H" 


s 


P. H" 


S 


P.Vs" 


Vol- 
ume 


^1 


























t3 


a 


ft 


1 


a 


ft 


'^ 


a 


ft 


'? 


a 


ft 


J- 


a 


ft 


ftl 


a 


ft 




U.Z 


ft 


,£J 


fti 


ft 


.£3 


fti 


ft 


.c 


ai 


ft 


ji 


fti 


p 


.£3 


ft 


JH 






H^ tf 


pq 


H^ 


Ph 


pq 


H^ 


p^ 


pq 


H^ 


Pi 


ffl 


H^ 


rt 


m 


H^ 


rt 


« 


16000 


1000 


2366 


108 


1.550 


2690 


123 


2.072 


2940 


134 


2.596 


3175 


145 


3.150 


3400 


155 


3.715 


3610 


164 


4.337 


17600 


1100 


2490 


113 


1.825 


2780 


127 


2.392 


3O40 


138 


2.967 


3267 


149 


3.560 


mc 


158 


4.160 


367C 


16714.800 


19200 


1200 


2600 


118 


2.172 


2925 


133 


2.770 


3125 


142 


3.360 


3360 


1531 4.000 


3575 


163 


4.655 


3763 


171 


5.318 


2()8()() 


i30(: 


2736 


124 


2.56C 


3000 


137 


3.175 


3237 


147 


3.817 


3475 


158 4.500 


3675 


167 


5.187 


3865 


176 


58.80 


22400 


1400 


2846j 129 


2.980 


3107 


141 


3.630 


3310 


151 


4.29£ 


3573 


1631 5.025 


375C 


171 


5.750 


3965 


180 


65.10 


24000 


150C 


2987 136 


3.482 


3226 


147 


4.168 


3460 


157 


4.885 


3650 


166 5.620 


3860 


176 


6.370 


406C 


185 


7.160 


25600 


1600 


3130 142 


4.00C 


3350 


153 


4.747 


3565 


162 


5.475 


3765 


171 6.255 


3960 


180 


7.045 


4160 


189 


7.870 


27200 


170C 


3270' 149 


4.585 


3475 


158 


5.368 


3680 


168 


6.155 


3885 


177; 6.95C 


1055 


184 


7.820 


1250 


193 


86.70 


28800 


1800 


3410; 155 


5.340 


3607 


164 


6.087 


3810 


173! 6.92C 


1010 


183: 7.750 


1180 


19C 


8.787 


4350 


198 


9.590 


30400 


190C 


3546. 161 


5.950 


3730 
3860 


170 


6.850 


3935 


179 7.699 


4120 


1871 8.600 


4320 


197 


9.51C 


4455 


203 


10.4 


32000 


2000 


3700 168 


6.750 


176 


7.69C 


1050 


184 8.58C 


1255 


194' 9.560 


1423 


201 


10.5 


4580 


20S 


11.4 


33600 


2100 


3850: 175 


7.600 


4000 


182 


8.600 


4210 


191 9.475 


1350 


19810.5 


4535 


206ill.5 


4680 


213 


12.5 


35200 


2200 


400C 


182 


8.520 


1168 


■189 


9.625 


4320 


197110.6 


4500 


20511.6 


4670 


213 


12.7 


4800 


219 


13.7 


36800 


2300 








4323 


197 


10.6 


4450 


20311.6 


1628 


21012.7 


4770 


217 


13.9 


4930 


224 


15.0 


38400 


2400 








4460 


203 


11.5 


4620 


21012.9 


1740 


21614.0 


4920 


224 


15.2 


5045 


22S 


16.24 


40000 


250f 








4600 


2()<j 


13.0 


472(1 


21514.2 


1880 


22215.3 


5036 


229 


16.49 


5170 


235 


17.62 


41600 


2600 














4910 


223J15.6 


5000 


237il6.80 


5180 


236 


18.05 


5325 


242 


19.20 


44800 


280(: 














il8(l 


236,18.55 


i280 


240;i9.98 


5435 


247 


21.18 


5510 


251 


22.62 


48000 


3000 














5485 


24921.96 


5610 


255 23.53 

i 


5650 


257 


24.76 


5840 


226 


26.25 



Vol- 
ume 


^ . 
o > 


S. P. 1" 


S. P. IK" 


S. P. IVi" 


S. P. IH" 


S. P. 2" 


S. P. 2H" 


ftl 




ftl 


a 

ft 


ft 


ft-S 

■^1 


a 

ft 


ft 


t3 
ftS^ 


a 
ft 


ft 


T3 


a 
ft 


i 


fta^ 


a 
ft 


ft 






H^ 


rt PQ 


Eh^ 


Ph 


pq 


rt 


pq 


H^ 


(A 


pq 


H^ 


K 


pq 


H^ 


p^ 


m 


19200 


1200 


3955 


1 
180 6.045 


4152 


189 


7.400 


4470 


203 


8.965 


4950 


225 


10.5 


5230 


236112.2 


5750 


262 


15.8 


2030(1 


1300 


4()5(J 


184 6.595 


4380 


199 


8.070 


4550 


207 


9.637 


5024 


228 


11.3 


5295 


241113.0 


582(1 


265 


16.64 


22400 


1400 


4143 


188 7.247 


4465 


203 


8.808 


1700 


212 


10.4 


5105 


232 


12.1 


535C 


24314.0 


590C 


263!l7.68 


24000 


1500 


425C 


193 7.957 


4570 


208 


9.560 


4850 


221 


11.2 


5180 


236 


13.0 


5450 


248!l4.9 


5950 


271 


18.80 


25600 


1600 


4325 


197 8.7K 


4652 


212 


10.4 


4950 


225 


12.1 


5245 


239 


13.9 


5550 


25215.9 


6025 


274 


19.90 


27200 


1700 


4437 


201] 9.545 


4750 


216 


11.4 


5040 


229 


13.2 


5330 


243 


15.0 


5625 


256,16.98 


6100 


277 


21.00 


28800 


180C 


4527 


20610.4 


4846 


221 


12.3 


5110 


232 


14.2 


54 IC 


246 


16.20 


5700 


259:18.16 


6195 


282 


22.35 


3040(] 


190C 


4613 


21011.4 


4945 


225 


13.3 


5230 


238 


15.3 


552C 


251 


17.37 


5780 


263119.43 


6265 


285 


23.68 


3200C 


2000 


4743 


21512.4 


5075 


231 


14.4 


5325 


242 


16.45 


562C 


255 


18.65 


5860 


267i20.80 


6365 


289125.10 


33600 


2100 


4850 


22113.5 


5145 


234 


15.6 


5440 


247 


17.73 


5724 


260 


20.00 


5955 


271122.18 


6475 


294126.80 


3520C 


2200 


4970 


22614.7 


5256 


239 


16.82 


5550 


252 


19.10 


5790 


264 


21.38 


6050 


275'23.61 


6550 


298|28.40 


3680C 


23()( 


5()9(: 


231116.67 


5370 


244 


18.21 


5630 


256 


20.47 


590(1 


268 


22.90 


6150t 280|25.20 


mo 


30130.20 


38400 


2400 


5210 


23717.39 


5480 


249 


19.67 


5750 


261 


22.00 


6025 


274 


24.46 


6270| 285:26.90 


6700 


305 32.00 


40000 


250C 


534C 


24318.89 


5610 


255 


21.12 


5850 


266 


23.60 


6100 


277 


26.10 


6343j 28928.72 


6800 


309 


33.80 


41600 


260C 


54851 24920.46 


5743 


261 


22.90 


5980 


272 


25.35 


6200 


282 


27.85 


6460i 293 30.65 


6880 


313 


35.80 


44800 


280( 


5710 260:24.08 


5960 


271 


26.41 


6230 


283 


29.15 


646C 


293 


31.85 


66501 303 34.60 


7090 


322 


40.10 


48000 


300C 


5970' 27227.70 


6200 


282 


30.40 


6460 


294 


33.36 


6675 


304 


36.10 


6900 314 39.08 


7295 


332 


44.90 


51200 


320C 


62301 283131.90 


6475 


294 


34.90 


6730 


306 


37.95 


6920 


315 


40.80 


7135 324 43.90 


7530 


343 


50.00 


54400 


3400 


6580 


299136.80 


6740 


307 


39.92 


6960 


316 


43.07 


7150 


325 


46.25 


7355 335149.30 


7750 


353 


55.70 


57600 


3600 


6815 


31041.92 


7020 


319 


45.30 


7200 


327 


48.07 


7440 


339 


51.99 


7600 346:55.38 


8020 


365 


61.80 


60800 


3800 


7105 


32347.90 


7350 


334 


51.60 


7475 


340 


54.92 


7660 


349 


58.37 


7840 357 61.60 


8220 


374 


69.00 



286 



HEATING AND VENTILATION 



CAPACITY TABLE 
Table XIII. — No. 160 Single Inlet Steel Plate Fan — Type S 







S 


P. H" 


S 


P. Vs" 


S 


P. 3-^" 


S 


P. ys" 


S 


P. H" 


S. P. ys" 


Vol- 
ume 


+o 
























3-;^ 


-a 


B 


ft 


t3 


a 


a 


t3 


a 


a 


'^ 


a 


a 


? 


a 


a 


y 


a 


a 




^ > 


aSJ 


d 


rC 


aj; 


d. 


js 


ai 


a 


^ 


al 


a 


JS 


a J) 


a 


rG 


a«> 


a 


M 






hS 


rt 


ffl 


H^ 


^ 


pq 


H^ 


rt 


PQ 


rH CO 


« 


pq 




P^ 


pq 


H& 


« 


pq 


20250 


1000 


2366 


94 


1.957 


2690 


107 


2.615 


2940 


117 


3.28 


3175 


127 


3.98 


3400 


135 


4.69 


3610 


144 


5.48 


22275 


1100 


2490 


99 


2.31 


2780 


111 


3.025 


3040 


121 


3.75 


3267 


130 


4.5 


348t 


139 


5.25 


367t 


146 


6.08 


24300 


1200 


2600 


104 


2.75 


2925 


116 


3.505 


3125 


125 


4.25 


336C 


134 


5.06 


3575 


142 


5.89 


376.: 


15C 


6.72 


26325 


130t 


2736 


109 


3.23 


3060 


119 


4.01 


3237 


12t 


4.82 


3475 


138 


5.68 


3675 


146 


6.55 


3865 


154 


7.44 


28350 


140t 


2846 


113 


3.77 


3107 


124 


4.59 


331C 


132 


5.43 


3573 


142 


6.35 


3750 


m 


7.26 


3965 


158 


8.2 


30375 


1500 


2987 


119 


4.40 


3226 


128 


5.27 


3460 


137 


6.17 


3650 


145 


7.1 


3860 


154 


8.05 


4060 


162 


9.05 


32400 


1600 


3130 


125 


5.06 


3350 


133 


5.99 


3565 


142 


6.92 


3765 


150 


7.91 


3960 


158 


8.9 


416C 


166 


9.94 


34425 


1700 


3270 


130 


5.78 


3475 


138 


6.79 


3680 


147 


7.77 


3885 


1.55 


8.78 


4055 


162 


9.88 


425C 


169 


10.93 


36450 


1800 


3410 


136 


6.75 


3607 


144 


7.68 


3810 


152 


8.725 


401C 


16C 


9.8 


4180 


167 


10.1 


4350 


173 


12.1 


38475 


1900 


3546 


141 


7.52 


373C 


148 


8.67 


3935 


157 


9.71 


4120 


164 


10.90 


4320 


172il2.0 


4455 


178 


13.1 


40500 


200C 


370C 


147 


8.54 


3860 


154 


9.71 


4050 


161 


10.83 


4255 


17C 


12.1 


4423 


176|13.2 


4580 


183 


14.4 


42525 


2100 


3850 


153 


9.60 


4000 


159 


10.85 


4210 


167 


11.97 


4350 


173 


13.3 


4535 


18114.6 


4680 


187 


15.8 


44550 


2200 


4000 


159 


10.74 


4168 


166 


12.17 


4320 


172 


13.40 


4500 


179 


14.7 


4670 


18616.0 


480C 


191 


17.3 


46575 


2300 








4323 


172 


13.44 


4450 


177 


14.70 


4623 


184 


16.1 


4770 


190117.5 


493C 


196 


18.9 


48600 


240f 








446C 


178 


14.55 


4620 


184 


16.30 


4740 


18£ 


17.7 


4920 


196119.2 


5045 


201 


20.5 


50625 


2500 








4600 


183 


16.40 


4720 


188 


17.90 


4880 


194 


19.4 


5036 


200120.8 


5170 


206 


21.3 


52650 


2600 














4910 


196 


19.80 


5000 


199 


21.3 


5180 


206122.8 


5325 


212 


24.3 


56700 


2800 














5180 


206 


23.4 


5280 


21C 


25.2 


5435 


216 


26.5 


5410 


220 


28.6 


60750 


3000 




1 








5485 


218 


27.8 


5610 


223 


29.7 


5650 


225 


31.3 


5840 


232 


33.1 







S. P. 1" 


S. P. IK" 


S. P. IM" 


S. P. IH" 


S. P. 2" 


s. P. 2y2" 


Vol- 
ume 
















a1 


a 


a 


"? 


a 


a 


'S 


a 


a 


"^ 


a 


a 


1 


a 


a 


'^ 


a 


a 




a 


pC3 


ai 


a 


,£3 


aS 


a 


rG 


a35 


a 


j3 


aS 


a 


^ 


aS 


a 


,£1 






H^ 


« 


pq 


H^ 


P5 


pq 


H^ 


« 


pq 


H^ 


rt 


pq 


H^ 


Pi 


PQ 


H^ 


rt 


pq 


24300 


1200 


3955 


158 


7.64 


4152 


166 


9.35 


4470 


178 


11.3 


4950 19713.3 


5230 208 


15.4 


5750 


229 


20.0 


26325 


1300 


405C 


161 


8.33 


138C 


175 


10.2 


455C 


182 


12.2 


5024 


20014.3 


5295; 211 


16.5 


582t 


232 


21.1 


28350 


1400 


4143 


165 


9.16 


4465 


178 


11.1 


470C 


187 


13.2 


5105 


20315.3 


5350 213 


17.7 


590C 


235 


22.4 


30375 


1500 


4250 


169 


10.04 


457C 


182 


12.1 


485C 


193 


14.2 


5180 


20616.4 


5450; 217 


18.8 


595C 


237 


23.7 


32400 


1600 


4325 


172 


11.0 


4652 


186 


13.2 


4950 


197[15.3 


5245; 209,17.6 


5550 222 


20,1 


6025 


240 


25.2 


34425 


1700 


4437 


177 


12.0 


4750 


189|14.4 


5040 


20016.6 


5330 21219.0 


5625! 224 


21.5 


6100 


243 


26.6 


36450 


1800 


4527 


18C 


13.1 


4846 


193115. 6 


5110 


203 17.9 


5410 216(20.4 


5700: 227 


22.9 


6195 


247 


28.3 


38475 


1900 


4613 


184 


14.4 


4945 


197 


16.8 


5230 


20819.3 


5520 220|21.9 


5780| 230 


24.5 


6265 


249 


29.9 


40500 


2000 


4743 


18C 


15.7 


5075 


202 


18.2 


5325 


212 20.8 


5620; 224 23.5 


5860 233 


26.3 


6365 


253 


31.8 


42525 


2100 


4850 


193 


17.0 


5145 


205 


19.7 


5440 


216 22.5 


5724 228125.3 


59551 237 


28.1 


6425 


257 


33.8 


44550 


2200 


4970 


198 


18.6 


5256 


209 


21.3 


5550 


22124.1 


57901 23027.0 


6050 241 


29.8 


6550 


261 


35.9 


46575 


2300 


5090 


203 


21.10 


5370 


214 


23.1 


5630 


224 25.9 


5909 235:28.9 


6150 245 


31.9 


6610 


263 


38.1 


48600 


2400 


5210 


208 


22.0 


5480 


218 


24.9 


5750 


229127.8 


6025' 24030.9 


6270; 250 


34.0 


6700 


267 


40.4 


50625 


250C 


5310 


213 


23.9 


5610 


224 


26.7 


5850 


233 29.8 


6100 24333.0 


6343 252 


36.3 


6800 


271 


42.8 


52656 


260C 


5485 


218 


24.8 


5740 


229 


28.9 


5980 


238 


32.0 


3200 24735.2 


5460 257 


38.7 


6880 


274 


45.3 


5670C 


2800 


5710 


228 


30.4 


5960 


238 


33.4 


6230 


248 


36.8 


6460) 257 40.3 


6650 265 


43.7 


7090 


282 


50.8 


60750 


3000 


5970 


238 


35.0 


6200 


247 


38.4 


6460 


257 


42.2 


6675i 26545.7 


6900; 274 


49.3 


7295 


290 


56.7 


64800 


3200 


6230 


252 


40.3 


6475 


258 


44.2 


6730 


268 


47.9 


6920 27651.6 
7150! 285:58.5 


7135 284 


55.4 


7530 


300 


63.0 


68850 


3400 


6580 


262 


46.5 


6740 


268 


50.5 


6960 


277 


54.4 


7355 293 
7600 303 


62.4 


7750 


308 


70.3 


72900 


3600 


6815 


272 


53.0 


7000 


279 57.3 


7200 


287 


61.6 


74401 29665.5 


70.0 


8020 


320 


78.0 


76950 


3800 


7105 


283 


60.5 


7350 


29265.2 


7475 


297 


69.4 . 


7660 30573.7 

1 j 


7840 312 


77.8 


8220 


328 


87.0 



APPENDIX 



287 



STATIC PRESSURE TABLES FOR NIAGARA CONOIDAL FANS^ 

Table XIV. — No. 3 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 
total 


Vi" 


S. P. 


H"Q.-P. 


M"S.P. 


H" S. P. 


Vi" S. P. 


J^"S.P. 


a 




a 




a 




a 




a 




a 




mm. 


per min. 


press. 


ft 


ft 


ft 


ft 


ft 


s 


ft 


^ 


ft 
f4 


ft 


ft 


ft 


1000 
1100 
1200 


1310 
1440 
1570 


.063 
.076 
.090 


387 

384 
387 


.09 
.11 
.12 


483 
477 
477 


.15 
.16 
.17 


557 


.23 














1300 
1400 
1500 


1710 
1840 
1970 


.106 
.122 
.141 


393 
400 
410 


.14 
.16 
.18 


470 
473 

477 


.18 
.20 
.23 


550 
547 
543 


.25 
.26 

.28 


623 
617 
613 


.32 
.33 
.35 


687 
680 


.42 
.43 


743 


.52 


1600 
1700 
1800 


2100 
2230 
2360 


.160 
.180 
.202 


420 
430 
443 


.21 
.24 

.28 


480 
490 
500 


.25 
.28 
.32 


547 
550 
553 


.31 
.34 
.37 


610 
607 
610 


.37 
.40 
.43 


673 
670 
667 


.45 
.48 
.51 


733 
727 
723 


.54 
.56 
.59 


1900 
2000 
2100 


2490 
2630 
2760 


.225 
.250 
.275 


457 
470 
483 


.31 
.35 
.39 


510 
520 
530 


.35 
.40 
.45 


560 
570 

580 


.41 
.45 
.50 


613 
617 
623 


.47 
.52 
.56 


667 
667 
670 


it 

.63 


720 
720 
720 


.62 
.66 
.71 


2200 
2300 
2400 


2890 
3020 
3150 


.302 
.330 
.360 


497 
513 
527 


.44 
.49 
.55 


543 
557 
570 


.50 
.55 
.61 


590 
600 
610 


.55 
.61 
.67 


633 
643 
650 


.61 
.67 
.73 


677 
683 
690 


.68 
.73 
.80 


723 

727 
733 


.76 
.81 

.87 


2500 
2600 
2800 


3280 
3410 
3670 


.390 
.422 
.489 


543 
560 
590 


.60 
.67 
.81 


583 
597 
623 


.67 

.74 
.89 


623 
633 
660 


.74 
.81 
.96 


660 
673 
693 


.80 

.88 

1.04 


700 
710 
730 


.86 

.94 

1.10 


740 
747 
767 


.94 
1.02 
1.17 


3000 
3200 
3400 


3940 
4190 
4460 


.560 
.638 
.721 


623 


.99 


657 


1.04 


687 
717 


1.14 
1.33 


720 

747 


1.22 
1.42 


753 
780 
807 


1.29 
1.50 
1.75 


780 
810 
833 


1.36 
1.58 
1.84 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add for 
total 
press. 


I" S. P. 


1K"S.P. 


1M"S.P. 


IK" s. p. 


2" S. P. 


21.^" S. P. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


a 








rt 


M 


p^ 


W 


rt 


w 


^ 


w 


« 


w 


rt 


W 


1300 


1710 


.106 


820 


.58 






















1400 


1840 


.122 


810 


.59 


920 


.80 


1027 


1.00 














1500 


1970 


.141 


800 


.62 


913 


.81 


1017 


1.04 


1110 


1.25 










1600 


2100 


.160 


793 


.64 


903 


.84 


1007 


1.06 


1100 


1.29 


1190 


1 . 53 






1700 


2230 


.180 


783 


.66 


893 


.86 


997 


1.09 


1087 


1.32 


1177 


1.58 


1343 


2.13 


1800 


2360 


.202 


777 


.68 


883 


.89 


983 


1.12 


1077 


1.35 


1167 


1.61 


1330 


2.16 


1900 


2490 


.225 


773 


.71 


877 


.92 


977 


1.14 


1067 


1.39 


1157 


1.65 


1317 


2.20 


2000 


2630 


.250 


770 


.75 


873 


.95 


970 


1.17 


1057 


1.42 


1143 


1.68 


1 303 


2.24 


2100 


2760 


.275 


770 


.79 


867 


.99 


960 


1.22 


1050 


1.46 


1133 


1.73 


1297 


2.29 


2200 


2890 


.302 


767 


.84 


863 


1.03 


953 


1.25 


1040 


1.50 


1127 


1.76 


1287 


2.33 


2300 


3020 


.330 


770 


.89 


860 


1.08 


950 


1.30 


1033 


1.54 


1120 


1.81 


1270 


2.38 


2400 


3150 


.360 


773 


.95 


860 


1.13 


947 


1.35 


1027 


1.59 


110711.85 


1263 


2.43 


2500 


3280 


.390 


777 


1.03 


860 


1.20 


943 


1.41 


1023 


1.64 


1103 1.91 


1253;2.49 


2600 


3410 


.422 


783 


1.09 


863 


1.26 


940 


1.47 


1020 


1.70 


1097 


1 96 


1247 2.54 


2800 


3670 


.489 


800 


1.25 


870 


1.43 


943 


1.63 


1013 


1.84 


1090 


2.10 


1233 2.67 


3000 


3940 


.560 


820 


1.44 


883 


1.61 


950 


1.81 


1020 


2.02 


1087 


2.25 


12272.82 


3200 


4190 


.638 


837 


1.65 


900 


1.83 


960 


2.02 


1023 


2.23 


1090 


2.47 


1217 3.00 


3400 


4460 


.721 


863 


1.90 


920 


2.06 


980 


2.26 


1033 


2.47 


1093 


2.69 


1213 


3.21 


3600 


4730 


.810 


883 


2.18 


943 


2.34 


997 


2.53 


1050 


2.76 


1107 


2.96 


1220 


3.48 


3800 


4990 


.900 










1017 


2.84 


1067 


3.04 


1117 


3.28 


1227 


3.76 


4000 


5250 


1.000 














1087 


3.39 


1133 


3.60 


1233 


4.10 



From ''Fan Engineering," Buffalo Forge Co. 



288 



HEATING AND VENTILATION 



Table XV. — No. 33^ Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 
total 


H" s. P. 


H"S.F. 


H" 


S.P. 


ys" 


S.P. 


M"S.P. 


Vs" S. P. 


a 




B 




a 




a 




a 




a 




min. 


per min. 


press. 


0. 










0. 


ft 


S 


ft 


ft 


ft 


ft 

a 


1000 
1100 
1200 


1790 
1970 
2140 


.063 
.076 
.090 


332 

329 
332 


.13 

.14 
.16 


414 
409 
409 


.20 
.21 
.23 


477 


.32 














1300 
1400 
1500 


2320 
2500 
2680 


.106 
.122 
.141 


337 
343 
352 


.18 
.21 
.24 


403' .25 
406j .28 
409, .31 


472 
469 
466 


.33 

.36 
.38 


534 
529 
526 


.43 
.45 

.48 


589 
583 


.57 
.59 


637 


.71 


1600 
1700 
1800 


2860 
3040 
3210 


.160 
.180 
.202 


360 
369 
380 


.28 
.32 
.37 


412 
422 
429 


.34 
.49 
.33 


469 
472 
474 


.42 
.46 
.51 


523 
520 
523 


.51 
.55 
.59 


577 
574 
572 


.62 
.65 
.69 


629 
623 
620 


.73 

.77 
.80 


1900 
2000 
2100 


3390 
3570 
3750 


.225 
.250 
.275 


392 
403 
414 


.42 
.48 
.53 


437 
446 
454 


.48 
.54 
.61 


480 
489 
497 


.56 
.62 
.68 


526 
529 
534 


.64 
.70 
.76 


572 
572 
574 


.74 
.79 
.86 


617 
617 
617 


.85 
.90 
.96 


2200 
2300 
2400 


3930 
4110 
4290 


.302 
.330 
.360 


426 
440 
452 


.59 
.67 
.74 


466 
477 
489 


.68 
.75 
.83 


506 
514 
523 


.75 
.83 
.91 


543 
552 
557 


.83 
.91 
.99 


580l .92 
586' 1.00 
592jl.09 


620 
623 
629 


1.03 
1.10 
1.18 


2500 
2600 
2800. 


4470 
4640 
5000 


.390 
.422 
.489 


466 
480 
506 


.82 

.91 

1.10 


500 
612 
534 


.91 
1.01 
1.21 


534 
543 
566 


1.01 
1.10 
1.31 


566 1.08 
577:1.19 
594 1.41 


60o'l.l7 
609 1.27 
626 1.50 


634 
640 
657 


1.27 
1.39 
1.59 


3000 
3200 
3400 


5360 
5720 
6070 


.560 
.638 
.721 


534 


1.35 


563 


1.42 


589 
614 


1.56 
1.81 


617jl.65 
640!l.94 


646 1.75 
669 2.05 
692,2.38 


669|l.85 
694 2.16 
714j2.50 



Outlet 

velocity, 

ft. per 

min. 


Capacity, 

cu. ft. 

air 

per min. 


Add 

for 

total 

press. 


1" S. P. 


1M"S.P. 


IK" S.P. 


1M"S. P. 


2" S. P. 


2K" S. P. 


a 
ft 


ft 


a 
ft 


a 


a 
ft 


ft 


a 
ft 
p? 


a 


a 
ft 
p^ 


ft 


a 
ft 


ft 


1300 
1400 
1500 


2320 
2500 
2680 


.106 
.122 
.141 


703 
694 
686 


.78 
.81 
.84 


789 
783 


1.08 
1.10 


880 
872 


1.36 
1.41 


952 


1.70 










1600 
1700 
1800 


2860 
3040 
3210 


.160 
.180 
.202 


680 
672 
666 


.86 
.89 
.93 


774^1.15 
766 1.17 
757|1.21 


863 
854 
843 


1.45 

1.48 
1.52 


943 
932 
923 


1.75 
1.79 
1.84 


1020 

1009 
1000 


2.08 
2.14 
2.19 


1151 
1140 


2.89 
2.94 


1900 
2000 
2100 


3390 
3570 
3750 


.225 
.2.50 
.275 


663 
660 
660 


.97 
1.02 
1.08 


752 1.25 
749 1.30 
743 1.35 


837! 1.56 
83111.59 
823,1.65 


914 
906 
900 


1.89 
1.94 
1.99 


992 2.24 
980 2.29 
972 2.35 


1129 
1117 

nil 


2.99 
3.05 
3.11 


2200 
2300 
2400 


3930 
4110 
4290 


.302 
.330 
.360 


657 1.14 
660 1 . 22 
663 1.30 


740 1.40 
737 1.47 
737 1 . 53 


817' 1.70 
814 1.77 

812 1.84 

1 


892 
886 
880 


2.03 
2.10 
2.17 


966 2.40 
960 2.46 
949 2.52 


1103 
1089 
1083 


3.17 
3.23 
3.31 


2500 
2600 
2800 


4470 
4640 
5000 


.390 
.422 
.489 


666 1.40 
672 1.48 
686 1.70 


737 1.63 
740 1 . 72 
746 1.95 


809 1.91 
806 2.00 
809 2.22 


877 
874 
869 


2.23 
2.32 
2.50 


946 
940 
934 


2.60 
2.67 
2.86 


1074 
1069 
1057 


3.38 
3.46 
3.63 


3000 
3200 
3400 


5360 
5720 
6070 


.560 
.638 
.721 


703 1.96 
717 2.24 
740 2.59 


757 2.19 
772 2.49 
789 2.81 


814'2.46 
823 2.75 
840 3.08 


874' 2. 74 
877 3 . 04 
886 3 . 36 


932 
934 
937 


3.06 
3.36 
3.66 


1052 '3. 84 
1043 4.08 
1040 4.36 


3600 
3800 
4000 


6430 
6790 
7140 


.810 

.900 

1.000 


757 


2.97 


809 


3.19 


854 
872 


3.44 
3.86 


900 3.75 
914 4.14 
932 4.61 


949 
957 
972 


4.03 
4.46 
4.90 


10464.73 
1052 5.12 
10575.59 



APPENDIX 



289 



Table XVI. — No. 4 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


K" S. P. 


M" S. P. 


y2" S. P. 


ya" S. P. 


H" S. P. 


Va" S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


p. 




p. 


S 


ft 


S 


ft 


ft 


ft 


ft 


ft 


a 


1000 
1100 
1200 


2330 
2570 
2800 


.063 
.076 
.090 


290 
288 
290 


.17 
.19 
.21 


363 
358 
358 


.26 
.28 
.30 


418 


.41 














1300 
1400 
1500 


3030 
3270 
3500 


.106 
.122 
.141 


295 
300 
308 


.24 
.28 
.32 


353 
355 
358 


.33 
.36 
.40 


413 
410 
408 


.44 
.47 
.50 


468 
463 
460 


.56 
.59 
.62 


515 
510 


.74 

.77 


558 


.92 


1600 
1700 
1800 


3730 
3970 
4220 


.160 
.180 
.202 


315 
323 
333 


.37 

.42 
.49 


360 
368 
375 


.45 
.50 
.56 


410 
413 
415 


.55 
.60 
.66 


458 
455 
458 


.66 
.71 

.77 


505 
503 
500 


.80 
.85 
.90 


550 
545 
543 


.96 
1.00 
1.05 


1900 
2000 
2100 


4430 
4670 
4900 


.225 
.250 
.275 


343 
353 
363 


.55 
.62 
.70 


383 
390 
398 


.63 
.71 
.80 


420 
428 
435 


.73 

.81 
.89 


460 
463 
468 


.84 

.92 

1.00 


500 
500 
503 


.96 
1.04 
1.12 


540 
540 
540 


1.11 
1.17 
1.26 


2200 
2300 
2400 


5130 
5370 
5600 


.302 
.330 
.360 


373 
385 
395 


.78 
.87 
.97 


408 
418 
428 


.88 

.98 

1.09 


443 
450 

458 


.98 
1.08 
1.19 


475 
483 

488 


1.08 
1.19 
1.30 


508 
513 
518 


1.21 
1.31 
1.42 


543 
545 
550 


1.35 
1.44 
1.55 


2500 
2600 
2800 


5830 
6070 
6530 


.390 
.422 
.489 


408 
420 
443 


1.07 
1.19 
1.44 


438 
448 
468 


1.19 
1.32 
1.58 


468 
475 
495 


1.32 
1.43 
1.71 


495 
505 
520 


1.41 
1.56 
1.84 


525 
533 

548 


1.53 
1.67 
1.95 


555 
560 
575 


1.67 
1.81 
2.08 


3000 
3200 
3400 


7000 
7460 
7930 


.560 
.638 
.721 


468 


1.76 


493 


1.86 


515 

538 


2.03 
2.37 


540 
560 


2.16 
2.53 


565 
585 
605 


2.29 
2.67 
3.11 


585 
608 
625 


2.42 
2.82 
3.27 



'J 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1" S. P. 


1M"S. P. 


IK" S. P. 


1%"S. P. 


2" S. P. 


2M" S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


ft 


a 


ft 


a 


a 
p4 


a 


a 
P^ 


a 


a 


ft 


ft 


S 


1300 
1400 
1500 


3030 
3270 
3500 


.106 
.122 
.141 


615 
608 
600 


1.03 
1.06 
1.09 


690 
685 


1.41 
1.44 


770 
763 


1.78 
1.84 


833 


2.23 










1600 
1700 
1800 


3730 
3970 
4220 


.160 
.180 
.202 


595 
588 
583 


1.13 
1.17 
1.22 


678 
670 
663 


1.50 
1.53 
1.58 


755 
748 
738 


1.89 
1.94 
1.94 


825 
815 
808 


2.29 
2.34 
2.40 


893 
883 
875 


2.72 
2.80 
2.87 


1008 
998 


3.78 
3.84 


1900 
2000 
2100 


4430 
4670 
4900 


.225 
.250 
.275 


580 
578 
578 


1.27 
1.33 
1.40 


658 
655 
650 


1.63 
1.70 
1.76 


733 

728 
720 


2.03 
2.08 
2.16 


800 
793 

788 


2.47 
2.53 
2.59 


868 
858 
850 


2.93 
2.99 
3.07 


988 
978 
973 


3.91 
3.99 
4.07 


2200 
2300 
2400 


5130 
5370 
5600 


.302 
.330 
.360 


575 

578 
580 


1.49 
1.59 
1.70 


648 
645 
645 


1.83 
1.92 
2.00 


7152.23 
7132.31 
7102.40 


780 
775 
770 


2.66 
2.74 
2.83 


845 
840 
830 


3.14 
3.22 
3.30 


965 
953 
948 


4.15 
4.23 
4.32 


2500 
2600 
2800 


5830 
6070 
6530 


.390 
.422 
.489 


583 
588 
600 


1.83 
1.94 
2.23 


645 
648 
653 


2.13 
2.24 
2.55 


708 2.50 
70512.61 
708 2.90 


768 
765 
760 


2.91 
3.03 
3.27 


828 
823 
818 


3.39 
3.49 
3.73 


940 
935 
925 


4.42 
4.51 

4.74 


3000 
3200 
3400 


7000 
7460 
7930 


.560 
.638 
.721 


615 
628 
648 


2.56 
2.93 
3.38 


663 
675 
690 


2.87 
3.25 
3.67 


713 
720 
735 


3.22 
3.59 
4.02 


765 
768 
775 


3.59 
3.97 
4.39 


815 
818 
820 


4.00 
4.39 
4.79 


920 
913 
910 


5.01 
5.33 
5.70 


3600 
3800 
4000 


8400 
8860 
9330 


.810 

.900 

1.000 


663 


3.87 


708 


4.16 


748 
763 


4.50 
5.04 


788 
800 
815 


4.90 
5.41 
6.02 


830 
838 
850 


5.27 
5.83 
6.40 


915 
920 
925 


6.18 
6.69 
7.30 



19- 



290 



HEATING AND VENTILATION 



Table XVII. — No. 4>^ Niagara Conoidal Fan (Type N) Capacities 
AND Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 
for 
total 


H" S. P. 


H" S. P. 


K" S. P. 


^^"S.P. 


H"S.T. 


J^"S.P. 


a 




a 




a 




a 




a 




a 




min. 


per mm. 


press. 


ft 


s 


ft 


ft 

w 


ft 


ft 

w 


ft 

pi 


ft 


ft 


S 


ft 

pi 


ft 


1000 
1100 
1200 


2950 
3250 
3540 


.063 
.076 
.090 


258 
256 
258 


.21 
.23 
.27 


322 

318 
318 


.33 
.35 
.38 


371 


.52 














1300 
1400 
1500 


3840 
4130 
4430 


.106 
.122 
.141 


262 
267 
273 


.30 
.35 
.40 


313 
316 
318 


.41 
.46 
.51 


367 
365 
362 


.55 
.59 
.63 


416 
411 
409 


0.71 
0.75 
0.79 


458 
453 


0.93 
0.97 


496 


1.17 


1600 
1700 
1800 


4720 
5020 
5310 


.160 
.180 
.202 


280 
287 
296 


.46 
.53 
.61 


320 
327 
333 


.57 
.64 
.71 


365 
367 
369 


.69 
.76 
.84 


407 
405 
407 


0.84 
0.90 
10.97 


449 
447 
445 


1.02 
1.07 
1.14 


489 
485 
482 


1.21 
11.27 
11.33 


1900 
2000 
2100 


5610 
5900 
6200 


.225 
.250 
.275 


305 
313 
322 


.69 
.79 

.88 


340 
347 
353 


.80 

.89 

1.01 


373 
380 
387 


.92 
1.02 
1.13 


409 
411 
416 


11.06 
11.16 
1.26 


445 
445 
447 


1.22 
1.31 
1.42 


480 
480 
480 


1.40 
1.48 
1.59 


2200 
2300 
2400 


6500 
6790 
7090 


.302 
.330 
.360 


331 
342 
351 


.98 
1.10 
1.23 


362 
371 
380 


1.12 
1.24 
1.38 


393 
400 
407 


1.24 
1.37 
1.51 


422 
429 
433 


1.37 
1.50 
1.64 


451 
456 
460 


1.53 
1.65 
1.80 


482 
485 
489 


1.71 
1.82 
1.96 


2500 
2600 
2800 


7380 
7680 
8270 


.390 

.422 
.489 


362 
373 
393 


1.35 
1.51 
1.82 


389 
398 
416 


1.50 
1.67 
2.00 


416 
422 
440 


1.67 
1.81 
2.17 


440 
449 
462 


1.79 
1.97 
2.33 


467 1.94 
473 2.11 

4872.47 


49312. 11 
498:2.29 
511 2.63 


3000 
3200 
3400 


8860 

9450 

10040 


.560 
.638 
.721 


416 


2.23 


438 


2.35 


4,58 
478 


2.57 
3.00 


480 2.73 
498 3.20 


502 2.90 
520 3.38 
5383.93 

i 


520 3.06 
540 3.57 
556 4.13 


Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 
for 
total 


1" S. P. 


1K"S.P. 


1H"S.P. 


1H"S.F. 


2" S. P. 


2H"S.P. 


a 




a 




a 




a 




a 




a 




mm. 


per min. 


press. 


ft 

P5 


S 


ft 


S 


ft 


ft 

w 


ft 


ft 

W 


ft 
f4 


ft 


ft 


ft 


1300 
1400 
1500 


3840 
4130 
4430 


.106 
.122 
.141 


.547 
540 
533 


1.30 
1.34 
1.38 


613 
609 


1.79 
1.82 


685 
678 


2.25 
2.33 


740 


2.82 










1600 
1700 
1800 


4720 
5020 
5310 


.160 
.180 
'.202 


529 
522 
518 


1.43 
1.48 
1.54 


602 
596 
589 


1.89 
1.93 
2.00 


671 
665 
656 


2.39 
2.45 
2.51 


733 
725 
718 


2.90 
2.96 
3.04 


793 3.44 
785 3.54 
778 3.63 


^896 
887 


4.78 
4.86 


1900 
2000 
2100 


5610 
5900 
6200 


.225 
.250 
.275 


516 1.60 
513 1.69 
513|1.78 


585 
582 
578 


2.07 
2.15 
2.23 


651 
647 
640 


2.57 
2.63 
2.74 


711 
704 
700 


3.12 
3.20 
3.28 


771 3.71 
762 3.79 
756 3.89 


878 
869 
865 


4.94 
5.04 
5.14 


2200 
2300 
2400 


6500 
6790 
7090 


.302 
.330 
.360 


511 1.89 
513'2.01 
5162.15 


576 
573 
573 


2.31 
2.43 
2.53 


636 
633 

631 

1 


2.82 
2.92 
3.04 


696 
689 
685 


3.36 
3.46 
3.59 


751 
747 
738 


3.97 
4.07 
4.17 


858 
847 
842 


5.25 
5.35 
5.47 


2500 
2600 
2800 


7380 
7680 
8270 


.390 
.422 
.489 


51812.31 
522 2.45 
53312.82 


573 
576 
580 


2.69 
2.84 
3.22 


629 
627 
629 


3.16 
3.30 
3.67 


682 
680 
676 


3.69 
3.83 
4.13 


736 
731 

727 


4.29 
4.42 
4.72 


836 
831 
822 


5.59 
5.71 
5.99 


3000 
3200 
3400 


8860 

9450 

10040 


.560 
.638 
.721 


547 

558 
576 


3.24 
3.71 

4.27 


589 
600 
613 


3.63 
4.11 
4.64 


633 
640 
653 


4.07 
4.54 
5.08 


680 
682 
689 


4.54 
5.02 
5.55 


725 

727! 
729 


5.06 
5.55 
6.06 


818 
811 
809 


6.34 
6.74 
7.21 


3600 
3800 
4000 


10630 
11220 
11810 


.810 

.900 

1.000 


589 


4.90 


629 


5.27 


665 
678 


5.69 
6.38 


700 
711 
725 


6.20 
6.85 
7.61 


738 
745 
756 


6.66 
7.37 
8.10 


813 
818 

822 


7.82 
8.46 
9.23 



APPENDIX 



291 



Table XVIIl.— No. 5 Niagara Conoid al Fan (Type N) Capacities 
AND Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 
for 
total 


K" S. P. 


H" S. P. 


K"S.P. 


H" S. P. 


Vi" S. P. 


K" s. p. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 

w 


ft 


ft 

w 


ft 


& 


1000 
1100 
1200 


3640 
4010 
4370 


.063 
.076 
.090 


232 
230 
232 


• .26 
.29 
.33 


290 
286 
286 


.41 
.44 
.47 


334 


.65 














1300 
1400 
1500 


4740 
5100 
5470 


.106 
.122 
.141 


236 
240 
246 


,38 
.43 
.50 


282 
284 
286 


.51 
.56 
.63 


330 
328 
326 


.68 
.73 

.78 


374 
370 
368 


.88 
.92 
.98 


412 
408 


1.15 
1.20 


446 


1.44 


1600 
1700 
1800 


5830 
6190 
6560 


.160 
.180 
.202 


252 
258 
266 


.57 
.66 
.76 


288 
294 
300 


.70 

.79 
.88 


328 
330 
332 


.86 

.94 

1.03 


366 
364 
366 


1.04 
1.11 
1.20 


404 
402 
400 


1.26 
1.33 
1.40 


440 
436 
434 


1.49 
1.57 
1.64 


1900 
2000 
2100 


6930 
7290 
7660 


.225 
.250 
.275 


274 
282 
290 


.86 

.97 

1.09 


306 
312 
318 


.99 
1.11 
1.24 


336 
342 
348 


1.14 
1.26 
1.39 


368 
370 
374 


1.31 
1.43 
1.56 


400 
400 
402 


1.50 
1.62 
1.75 


432 
432 
432 


1.73 
1.83 
1.96 


2200 
2300 
2400 


8010 
8380 
8750 


.302 
.330 
.360 


298 
308 
316 


1.'21 
1.36 
1.51 


326 
334 
342 


1.38 
1.55 
1.70 


354 
360 
366 


1.53 
1.69 
1.86 


380 
386 
390 


1.69 
1.85 
2.03 


406 
410 
414 


1.89 
2.04 
2.22 


434 
436 
440 


2.11 
2.25 
2.41 


2500 
2600 
2800 


9100 

9480 

10200 


.390 
.422 
.489 


326 
336 
354 


1.67 
1.86 
2.25 


350 
358 
374 


1.86 
2.06 
2.46 


374 
380 
396 


2.06 
2.24 
2.68 


396 
404 
416 


2.21 
2.43 

2.88 


420 
426 
438 


2.40 
2.60 
3.05 


444 
448 
460 


2.60 
2.83 
3.25 


3000 
3200 
3400 


10940 
11660 
12390 


.560 
.638 
.721 


374 


2.75 


394 


2.90 


412 
430 


3.18 
3.70 


432 
448 


3.38 
3.95 


452 
468 
484 


3.58 
4.18 
4.85 


468 
486 
500 


3.78 
4.40 
5.10 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 
for 
total 


V S. P. 


13^" S. P. 


1H"S. P. 


m" s. p. 


2" S. P. 


2}>i" S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


ft 


ft 


ft 


ft 
M 


ft 
P5 


ft 


ft 


ft 


ft 
p4 


a 


ft 


ft 


1300 
1400 
1500 


4740 
5100 
5470 


.106 
.122 
.141 


492 
486 
480 


1.60 
1.65 
1.71 


552 

548 


2.21 
2.25 


616 
610 


2.78 
2.88 


666 


3.48 










1600 
1700 
1800 


5830 
6190 
6560 


.160 
.180 
.202 


476 
470 
466 


1.76 
1.82 
1.90 


542 
536 
530 


2.34 
2.39 

2.47 


604 
598 
590 


2.95 
3.03 
3.10 


660 
652 
646 


3.58 
3.65 
3.75 


714 
706 
700 


4.25 
4.38 
4.48 


806 
798 


5.90 
6.00 


1900 
2000 
2100 


6930 
7290 
7660 


.225 
.250 
.275 


464 
462 
462 


1.98 
2.08 
2.19 


526 
524 
520 


2.55 
2.65 
2.75 


586 
582 
576 


3.18 
3.25 
3.38 


640 
634 
630 


3.85 
3.95 
4.05 


694 
686 
680 


4.58 
4.68 
4.80 


790 

782 
778 


6.10 
6.23 
6.35 


2200 
2300 
2400 


8010 

8380 

• 8750 


.302 
.330 
.360 


460 
462 
464 


2.33 

2.48 
2.65 


518 
516 
516 


2.85 
3.00 
3.13 


572 
570 
568 


3.48 
3.60 
3.75 


624 
620 
616 


4.15 
4.28 
4.44 


676 
672 
664 


4.90 
5.03 
5.15 


772 
762 
758 


6.48 
6.60 
6.75 


2500 
2600 
2800 


9100 

9480 

10200 


.390 
.422 
.489 


466 
470 
480 


2.85 
3.03 
3.48 


516 
518 
522 


3.33 
3.50 
3.98 


566 
564 
566 


3.90 
4.08 
4.53 


614 
612 
608 


4.55 
4.73 
5.10 


662 
658 
654 


5.30 
5.45 
5.83 


752 
748 
740 


6.90 
7.05 
7.40 


3000 
3200 
3400 


10940 
11660 
12390 


.560 
.638 
.721 


492 
502 
518 


4.00 
4.57 
5.27 


530 
540 
552 


4.48 
5.08 
5.73 


570 
576 

588 


5.03 
5.60 
6.28 


612 
614 
620 


5.60 
6.20 
6.85 


652 
654 
656 


6.25 
6.85 
7.48 


736 
730 

728 


7.83 
8.32 
8.90 


3600 
3800 
4000 


13120 
13850 
14580 


.810 

.900 

1.000 


530 


6.05 


566 


6.50 


598 
610 


7.03 

7.88 


630 
640 
652 


7.65 
8.46 
9.40 


664 
670 
680 


8.22 
9.10 
10.0 


732 
736 
740 


9.65 
10.5 
11.4 



292 



HEATING AND VENTILATION 



Table XIX. — No. 53^ Niagara Conoidal Fan (Type N) Capacities 
AND Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


H"S.P. 


Vs" S. P. 


V2" S. P. 


%" S. P. 


v^" s. p. 


%" S. P. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


ft 


a 


ft 


«" 


ft 


ft 


ft 


i 


ft 

p4 


ft 


ft 


d 


1000 
1100 
1200 


4410 
4850 
5290 


.063 
.076 
.090 


211 
209 
211 


.32 
.35 
.40 


264 
260 
260 


.49 
.53 

•.57 


304 


.78 














1300 
1400 
1500 


5730 
6170 
6620 


.106 
.122 
.141 


215 
218 
224 


.45 
.52 
.60 


257 
258 
260 


.62 
.68 
.76 


300 
298 
296 


.83 
.88 
.95 


340 
336 
335 


1.06 
1.12 
1.18 


375 

371 


1.40 
1.45 


406 


1.75 


1600 
1700 
1800 


7060 
7500 
7940 


.160 
.180 
.202 


229 
235 
242 


.69 
.80 
.92 


262 
267 
273 


.85 

.95 

1.06 


298 
300 
302 


1.04 
1.13 
1.25 


333 
331 
333 


1.26 
1.35 
1.46 


367 
366 
364 


1.52 
1.60 
1.70 


400 
397 
395 


1.81 
1.89 
1.98 


1900 
2000 
2100 


8380 
8820 
9260 


.225 
.250 
.275 


249 
256 
264 


1.04 
1.17 
1.32 


278 
284 
289 


1.19 
1.34 
1.50 


306 
311 
316 


1.38 
1.53 
1.68 


335 
336 
340 


1.59 
1.73 
1.88 


364 
364 
366 


1.82 
1.96 
2.12 


393 
393 
393 


2.09 
2.21 
2.37 


2200 
2300 
2400 


9700 
10140 
10590 


.302 
.330 
.360 


271 

280 
287 


1.47 
1.65 
1.83 


296 
304 
311 


1.67 
1.86 
2.05 


322 
327 
333 


1.85 
2.05 
2.25 


346 
351 
355 


2.05 
2.24 
2.45 


369 
373 
377 


2.28 
2.47 
2.68 


395 
397 
400 


2.55 
2.72 
2.92 


2500 
2600. 
2800 


11030 
11470 
12350 


.390 
.422 
.489 


297 
306 
322 


2.02 
2.25 

2.72 


318 
326 
340 


2.25 
2.49 
2.98 


340 
346 
360 


2.49 
2.71 
3.24 


360 
367 

378 


2.67 
2.94 
3.48 


382 
387 
398 


2.90 
3.15 
3.69 


404 
407 
418 


3.15 
3.42 
3.93 


3000 
3200 
3400 


13230 
14110 
15000 


.560 
.638 
.721 


340 


3.33 


358 


3.51 


375 
391 


3.84 

4.48 


393 
407 


4.08 
4.78 


411 
426 
440 


4.33 
5.05 

5.87 


426 
442 
455 


4.57 
5.33 
6.17 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


I" S. P. 


IK" S. P. 


1H"S.P. 


m" S. P. 


2" S. P . 


K2" S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


ft 


ft 


ft 


a 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


1300 
1400 
1500 


5730 
6170 
6620 


.106 
.122 
.141 


447 

442 
437 


1.94 
1.99 
2.07 


502 

498 


2.67 
2.72 


560 
555 


3.36 
3.48 


606 


4.21 










1600 
1700 
1800 


7060 
7500 
7940 


.160 
.180 
.202 


433 

427 
424 


2.13 
2.20 
2.30 


493 

487 
482 


2.83 
2.89 
2.99 


549 
544 
537 


3.57 
3.66 
3.75 


6004.33 
5934.42 

587 4.54 


649 
642 
636 


5.14 
5.29 
5.42 


733 

726 


7.14 
7.26 


1900 
2000 
2100 


8380 
8820 
9260 


.225 
.250 
.275 


422 
420 
420 


2.39 
2.52 
2.65 


478 
476 
473 


3.09 
3.21 
3.33 


533 
529 
524 


3.84 
3.93 
4.08 


582 4.66 
576 4.78 
573 4.90 


631 
624 
618 


5.54 
5.66 
5.81 


7r8 
711 
707 


7.38 
7.53 
7.68 


2200 
2300 
2400 


9700 
10140 
10590 


.302 
.330 
.360 


418 
420 
422 


2.82 
3.00 
3.21 


471 
469 
469 


3.45 
3.63 

3.78 


520 
518 
517 


4.21 
4.36 
4.54 


567 5.02 
564{5.17 
560 5.35 


615 
611 
604 


5.93 
6.08 
6.23 


702 
693 
689 


7.84 
7.99 
8.17 


2500 
2600 
2800 


11030 
11470 
12350 


.390 

.422 
.489 


424 
427 
437 


3.45 
3.66 
4.21 


469 
471 
475 


4.02 
4.24 
4.81 


515 
513 
515 


4.72 
4.93 
5.48 


558 
557 
553 


5.51 
5.72 
6.17 


602 
598 
595 


6.41 
6.59 
7.05 


684 
680 
673 


8.35 
8.53 
8.95 


3000 
3200 
3400 


132.30 
14110 
15000 


.560 
.638 
.721 


447 
456 
471 


4.84 
5.54 
6.38 


482 
491 
502 


5.42 
6.14 
6.93 


518 
524 
535 


6.08 
6.78 
7.59 


557 
558 
564 


6.78 
7.50 
8.29 


593 
595 
596 


7.56 
8.29 
9.04 


669 
664 
662 


9.47 
10.1 
10.8 


3600 
3800 
4000 


15880 
16760 
17640 


.810 

.900 

1.000 


482 


7.32 


515 

i 


7.87 


544 
555 


8.50 
9.53 


573 
582 
593 


9.26 
10.2 
11.4 


604 
609 
618 


9.95 
11.0 
12.1 


666 
669 
673 


11.7 
12.7 
13.8 



APPENDIX 



293 



Table XX. — No. 6 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Baromp:ter 



Outlet 

volocity, 

ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


H" S. P. 


H" S. P. 


H" S. P. 


^^"S.P. 


H" S. P. 


K" S. P. 


a 




a 




a 




B 




a 




a 




mm. 


per min. 


press. 




a 


a 


a 

K 


a 


a 
W 


a 


S 


a 


a 


a 


a 


1000 
1100 
1200 


5250 
5770 
6300 


.063 
.076 
.090 


193 
192 
193 


.37 

.42 
.48 


242 
238 
238 


.59 
.63 
.67 


278 


.93 














1300 
1400 
1500 


6820 
7350 
7870 


.106 
.122 
.141 


197 
200 
205 


.54 
.62 
.72 


235 
237 
238 


.73 
.81 
.91 


275 

274 
272 


.98 
1.05 
1.13 


312 
308 
307 


1.27 
1.33 
1.41 


344 
340 


1.60 
1.72 


372 


2.08 


1600 
1700 
1800 


8400 
8920 
9450 


.160 
.180 
.202 


210 
215 
222 


.82 

.95 

1.09 


240 
245 
250 


1.01 
1.13 
1.26 


274 

275 
277 


1.23 
1.35 
1.49 


305 
304 
305 


1.49 
1.60 
1.73 


337 
335 
334 


1.81 
1.91 
2.02 


367 
363 
362 


2.15 
2.25 
2.36 


1900 
2000 
2100 


9970 
10500 
11030 


.225 
.250 
.275 


228 
235 
242 


1.24 
1.40 
1.57 


255 
260 
265 


1.42 
1.59 
1.79 


280 
285 
290 


1.64 
1.82 
2.00 


307 
309 
312 


1.88 
2.06 
2.24 


334 
334 
335 


2.16 
2.33 
2.52 


360 
360 
360 


2.49 
2.63 
2.82 


2200 
2300 
2400 


11550 
12070 
12600 


.302 
.330 
.360 


248 
257 
263 


1.75 
1.96 
2.18 


272 
279 
285 


1.98 
2.21 
2.45 


295 
300 
305 


2.20 
2.43 
2.68 


317 
322 
325 


2.43 
2.66 
2.92 


339 
342 
345 


2.72 
2.94 
3.19 


362 
363 
367 


3.04 
3.23 
3.48 


2500 
2600 
2800 


13120 
13650 
14700 


.390 
.422 
.489 


272 
280 
295 


2.41 
2.68 
3.24 


291 
299 
312 


2.67 
2.96 
3.55 


312 
317 
330 


2.96 
3.22 
3.85 


33o'3.18 
3373.50 
347|4.14 


350 
355 
365 


3.45 
3.74 
4.39 


370 
374 
384 


3.74 
4.07 
4.68 


3000 
3200 
3400 


15750 
16790 
17850 


.560 
.638 
.721 


312 


3.96 


329 


4.18 


344 
359 


4.57 
5.33 


360 4.86 
373 5.69 


377 
390 
403 


5.15 
6.01 
6.98 


390 
405 
417 


5.44 
6.34 
7.35 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1" S. P. 


IH" S. P. 


1M"S.P. 


l^i"S.P. 


2" S. P. 


2iA" S. P. 


a 


a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


ft a 


a 


a 


a 

P^ 


S 


a 
P^ 


a 


5 


a 


a 
P^ 


a 


1300 
1400 
1500 


6820 
7350 
7870 


.106 
.122 
.141 


4102.31 
405 2.37 
400 2.46 


460 
457 


3.18 
3.24 


513 
509 


4.00 
4.14 


555 


5.00 










1600 
1700 
1800 


8400 
8920 
9450 


.160 
.180 
.202 


397*2.54 
392 2.62 

389 2.73 

1 


452 
447 
442 


3.36 
3.44 
3.56 


504 
499 
492 


4.25 
4.36 
4.47 


550 
544 
539 


5.15 
5.26 
5.40 


595 6.12 
589 6.30 
584 6.45 


672 
665 


8.50 

8.64 


1900 
2000 
2100 


9970 
10500 
11030 


.225 
.250 
.275 


387 2.85 
385 3.00 
385 3.16 


439 
437 
434 


3.67 
3.82 
3.96 


489 
485 
480 


4.57 
4.68 
4.86 


534 
529 
525 


5.55 
5.69 
5.83 


579 6.59 
57216.73 
5676.91 


659 
652 
649 


8.78 
8.96 
9.14 


2200 
2300 
2400 


11550 
12070 
12600 


.302 
.330 
.360 


384.3.35 
385 3.57 
387,3.82 


432 
430 
430 


4.11 
4.32 
4.50 


477 
475 
474 


5.00 
5.18 
5.40 


520 
517 
514 


5.98 
6.16 
6.37 


564 7.06 
560 7.24 
554:7.42 


644 
635 
632 


9.32 
9.50 
9.72 


2500 
2600 
2800 


13120 
13650 
14700 


.390 
.422 
.489 


389 4.10 
392 4.36 
400 5.00 


430 
432 
435 


4.79 
5.04 
5.73 


472 
470 
472 


5.62 
5.87 
6.52 


512 
510 
507 


6.55 
6.81 
7.34 


552 7.63 
549 7.85 

545 8.39 

1 


627 
624 
617 


9.94 
10.2 
10.7 


3000 
3200 
3400 


15750 
16790 
178.50 


.560 
.638 
.721 


410 
419 
432 


5.76 
6.59 
7.60 


442 
450 
460 


6.45 
7.31 

8.24 


475 
480 
490 


7.24 
8.06 
9.04 


510 8.06 
5128.93 
517 9.86 


544 
545 
547 


9.00 
9.86 
10.8 


614ill.3 
609 12.0 
607 12.8 


36001 

3800 

4000 


18900 
19950 
21000 


.810 

.900 

1.000 


442 


8.71 


472 


9.36 


499 
509 


10.1 
11.3 


525 11.0 
534 12.2 
544113.5 


554 
559 
567 


11.9 
13.1 
14.4 


610 
614 
617 


11:? 

:c.4 



294 



HEATING AND VENTILATION 



Table XXI. — No. 7 Niagara Conoidal Fan (Type N) Capacities ani> 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 

velocity, 

ft. 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


H" S. P. 


H" S. P. 


H"S.P. 


^^"S.P. 


H" S. P. 


ys"s.i\ 


a 




a 




a 




a 




a 




a 




per min. 


per mm. 


press. 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 


ft 

K 


1000 
1100 
1200 


7140 
7860 
8570 


.063 
.076 
.090 


166 
164 
166 


.51 
.57 
.65 


207 
204 
204 


.80 
.85 
.92 


239 


1.26 














1300 
1400 
1500 


9290 
10000 
10720 


.106 
.122 
.141 


169 
172 
176 


.74 
.85 
.98 


202 1.00 

203 1.10 

204 1.24 


236 1 . 34 
234' 1.43 
233 1.53 


267 
264 
263 


1.73 
1.81 
1.91 


294 2.26 
2922.34 


319 


2.83 


1600 
1700 
1800 


11430 
12150 
12860 


.160 
.180 
.202 


180 1.12 
184 1.29 
190,1.49 


206 1 . 37 
210 1.54 
214 1.72 


23411.68 
236|l.83 
237 2.02 


262 
260 
262 


2.03 
2.18 
2.36 


28912.46 
287:2.60 
286j2.75 


31412.93 
312i3.07 
310,3.21 


1900 
2000 
2100 


13570 
14290 
15000 


.225 
.250 
.275 


196 1.68 
202 1.90 
207,2.13 


219 1.93 
223 2.17 
227 2.44 


240 2.23 
244 2.47 
249 2.73 


263 2.56 

264 2.80 
267j3.05 


286 2.95 
286 3.18 
287j3.43 


3093.39 
3093.58 
309|3.84 


2200 
2300 
2400 


15720 
16430 
17150 


.302 
.330 
.360 


2132.38 
220 2.67 
226,2.97 


2332.70 
239 3.01 
244 3.33 


253 3.00 
2573.31 
262 3.64 


272 
276 
279 


3.31 
3.63 
3.97 


290 
293 
296 


3.70 
4.00 
4.34 


310 
312 
314 


4.13 
4.40 
4.73 


2500 
2600 
2800 


17860 
18580 
20000 


.390 

.422 
.489 


233 
240 
253 


3.27 
3.64 
4.41 


2503.64 
2564.03 
2674.83 


267' 4. 03 
2724.39 
283 5.24 


283 
289 
297 


4.33 

4.77 
5.64 


300 
304 
313 


4.70 
5.10 
5.98 


317 
320 
329 


5.10 

5.54 
6.37 


3000 
3200 
3400 


21430 
22860 
24290 


.560 
.638 
.721 


267 


5.39 


282 


5.68 


294 
307 


6.22 
7.25 


309 
320 


6.62 
7.74 


323 
334 
346 


7.01 
8.18 
9.51 


334 
347 
357 


7.40 
8.62 
10.0 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1" S. P. 


IH" S. P. 


1M"S.P.' 


1M"S.P. 


2" S. P. 


2K"S.P. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


ft 


ft 


ft 


S 


ft 


a 


ft 

c4 


ft 


ft 
P5 


ft 


ft 


ft 


1300 
1400 
1500 


9290 
10000 
10720 


.106 
.122 
.141 


352 
347 
343 


3.14 
3.23 
3.35 


394 
392 


4.33 
4.41 


440 
436 


5.44 
5.64 


476 


6.81 










1600 
1700 
1800 


11430 
12150 
12860 


.160 
.180 
.202 


340 3.46 
336 3.57 
333 3.72 


387 
383 
379 


4.58 
4.68 
4.85 


432 5.78 
4275.93 
422 6.08 


472 
466 
462 


7.01 
7.15 
7.35 


510 
504 
500 


8.33 
8.58 
8.77 


576 
570 


11.6 
11.8 


1900 
2000 
2100 


13.570 
14290 
15000 


.225 
.250 
.275 


332 
330 
330 


3.88 
4.08 
4.30 


376 
374 
372 


5.00 
5.19 
5.39 


419*6.22 
416 6.37 
4126.62 


457 7.55 
45317.74 
450j7.94 


496 
490 
486 


8.97 
9.16 
9.41 


564 
559 
556 


12.0 
12.2 
12.5 


2200 
2300 
2400 


15720 
16430 
17150 


.302 
.330 
.360 


329 
330 
332 


4.56 
4.86 
5.19 


370 
369 
369 


5.59 
5.88 
6.13 


409 6.81 
407 7.06 
406 7.35 


446^8.13 
443 8.38 
440 8.67 


483 
480 
474 


9.60 
9.85 
10.1 


552 
544 
542 


12.7 
12.9 
13.2 


2500 
2600 
2800 


17860 
18580 
20000 


.390 
.422 
.489 


333 
336 
343 


5.59 
5.93 
6.81 


36916.52 
370 6.86 
373 7.79 


4047.64 

403 7.99 

404 8.87 

1 


439 8.92 
4379.26 
434 10.0 


473 
470 
467 


10.4 
10.7 
11.4 


537 
534 
529 


13.5 
13.8 
14.5 


3000 
3200 
3400 


21430 
22860 
24290 


.560 
.638 
.721 


352 7.84 
359 8.97 
370 10.3 


379 
386 
394 


8.77 
9.95 
11.2 


407 9.85 
412 11.0 

420 12.3 

i 


437 11.0 
439 12.2 
443 13.4 


466 
467 
469 


12.3 
13.4 
14.7 


526! 15. 3 
522,16.3 
520 17.4 


3600 
3800 
4000 


25720 
27150 
28580 


.810 

.900 

1.000 


379 11.9 


404 


12.7 


427 
436 


13.8 
15.4 


45o'l5.0 
457 16.6 
466 18.4 


474 
479 
486 


16.1 
17.8 
19.6 


523!l8.9 
526:20.5 
529 22.4 



APPENDIX 



295 



Table XXII. — No. 8 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


Vi" S. P. 


H" S. P. 


Vi" S. P. 


H" S. P. 


^"S.P. 


%" S. P. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


p. 


ft 


0. 

f4 


a 


p. 


a 




a 
W 


a 


a 


a 


w" 


1000 
1100 
1200 


9330 
10270 
11200 


.063 
.076 
.090 


145 
144 
145 


.67 
.74 
.85 


18l'l.04 
179 1.11 
179 1.20 


209 


1.65 














1300 
1400 
1500 


12130 
13060 
14000 


.106 
.122 
.141 


148 
150 
154 


.96 
1.11 
1.27 


176'l.31 

178 1.44 

179 1.61 


206 
205 
204 


1.75 
1.87 
2.00 


234 
231 
230 


2.25 
2.36 
2.50 


258 
255 


2.95 
3.06 


279 


3.69 


1600 
1700 
1800 


14930 
15860 
16800 


.160 
.180 
.202 


158 
161 
166 


1.47 
1.69 
1.94 


180' 1.79 
1842.01 
188 2.25 


205 
206 
208 


2.19 
2.39 
2.64 


229 
228 
229 


2.66 
2.85 
3.08 


253 
251 
250 


3.21 
3.39 
3.59 


275 
273 
271 


3.82 
4.01 
4.19 


1900 
2000 
2100 


17730 
18660 
19600 


.225 
.250 
.275 


171 
176 
181 


2.20 
2.48 
2.79 


1912.52 
195; 2. 83 
1993.18 


210 
214 
218 


2.91 
3.23 
3.56 


230 
231 
234 


3.34 
3.66 
3.98 


250 
250 
251 


3.85 
4.15 
4.48 


27014.42 
270|4.68 
270 5.02 


2200 
2300 
2400 


20530 
21460 
22400 


.302 
.330 
.360 


186 
193 
198 


3.11 

3.48 
3.87 


204 
209 
214 


3.53 
3.93 
4.35 


221 
225 
229 


3.92 
4.33 

4.76 


238 
241 
244 


4.33 
4.74 
5.19 


254 
256 
259 


4.83 
5.22 
5.67 


271 
273 
275 


5.40 
5.75 
6.18 


2500 
2600 
2800 


23330 
24260 
26130 


.390 
.422 
.489 


204 
210 
221 


4.28 
4.76 
5.76 


219 
224 
234 


4.75 
5.26 
6.31 


234 
238 

248 


5.26 
5.73 
6.85 


248 
253 
260 


5.65 
6.23 
7.36 


263 
266 

274 


6.13 
6.66 
7.81 


278 
280 
288 


6.66 
7.23 
8.32 


3000 
3200 
3400 


28000 
29860 
31720 


.560 
.638 
.721 


234 


7.04 


246 


7.42 


258 
269 


8.13 
9.47 


270 
280 


8.64 
10.1 


283 
293 
303 


9.15 
10.7 
12.4 


293 
304 
313 


9.66 
11.3 
13.1 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1"S. P. 


IK" s. p. 


lyi" S.P. 


1%" S. P. 


2" S. P. 


2K"S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


a 


a 


a 


i 


a 


a 
W 


a 


a 


a 

p4 


a 


a 


a 


1300 
1400 
1500 


12130 
13060 
14000 


.106 
.122 
.141 


308 
304 
300 


4.10 
4.22 
4.37 


345 
343 


5.65 
5.76 


385 
381 


7.10 
7.36 


416 8.90 










1600 
1700 
1800 


14930 
15860 
16800 


.160 
.180 
.202 


298 
294 
291 


4.51 
4.66 
4.86 


339 
335 
331 


5.98 
6.11 
6.33 


378 
374 
369 


7.55 
7.74 
7.94 


413 9.15 
408 9 . 34 
404|9.60 


446 
441 
438 


10.9 
11.2 
11.5 


504 
499 


15.1 
15.4 


1900 
2000 
2100 


17730 
18660 
19600 


.225 
.250 
.275 


290 
289 
289 


5.06 
5.33 
5.61 


329 
328 
325 


6.53 
6.78 
7.04 


366 8.13 
3648.32 
360 8.64 


400 
396 
394 


9.86 
10.1 
10.4 


434 
429 

425 


11.7 
12.0 
12.3 


494 15.6 
489 15.9 
486 16.3 


2200 
2300 
2400 


20530 
21460 
22400 


.302 
.330 
.360 


288 
289 
290 


5.96 
6.35 

6.78 


324 
323 
323 


7.30 
7.68 
8.00 


358 8.90 
356 9.22 
355 9.60 


390 
388 
385 


10.6 
11.0 
11.3 


423 
420 
415 


12.6 
12.9 
13.2 


483' 16. 6 
476 16.9 
474 17.3 


2500 
2600 
2800 


23330 
24260 
26130 


.390 
.422 
.489 


291 
294 
300 


7.30 

7.74 
8.90 


323 
324 
326 


8.51 
8.96 
10.2 


354 
353 
354 


9.98 
10.4 
11.6 


384 
383 
380 


11.7 
12.1 
13.1 


414 
411 
409 


13.6 
14.0 
14.9 


470 
468 
463 


17.7 
18.1 
19.0 


3000 
3200 
3400 


28000 
29860 
31720 


.560 
.638 
.721 


308 
314 
324 


10.2 
11.7 
13.5 


331 
338 
345 


11.5 
13.0 
14.7 


356 
360 
368 


12.9 
14.3 
16.1 


383 
384 
388 


14.3 
15.9 
17.5 


408 
409 
410 


16.0 
17.5 
19.1 


460 
456 
455 


20.0 
21.3 
22.8 


3600 
3800 
4000 


33590 
35460 
37330 


.810 

.900 

1.000 


331 


15.5 


354 


16.6 


374 
381 


18.0 
20.2 


394 
400 
408 


19.6 
21.6 
24.1 


415 
419 
425 


21.1 
23.3 
25.6 


458 
460 
463 


24.7 
26.8 
29.2 



296 



HEATING AND VENTILATION 



Table XXIII. — No. 9 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 
cu. ft. 

air 


Add 

for 

total 


K" S. P. 


^^"S.P. 


H" S. P. 


H" S. P. 


K" S. P. 


K"S.P. 


a 




a 




a 




a 




a 




a 




imin. 


per mm. 


press. 


a 




ft 


a 


a 


ft 


a 


a 


a 


a 


a 


ft 

a 


1000 
1100 
1200 


1181.0 
12990 
14170 


.063 
.076 
.090 


129 
128 
129 


.84 

.94 

1.07 


161 
159 
159 


1.32 
1.41 
1.52 


186 


2.09 














1300 
1400 
1500 


15360 
16530 
17720 


.106 
.122 
.141 


131 
133 
137 


1.22 
1.40 
1.61 


157 
158 
159 


1.65 
1.82 
2.04 


183 
182 
181 


2.21 
2.37 
2.54 


208 2.85 
206 2.99 
205! 3. 16 


229 
227 


3.74 
3.87 


248 


4.67 


1600 
1700 
1800 


18900 
20080 
21250 


.160 
.180 
.202 


140 
143 
148 


1.86 
2.14 
2.45 


160 
163 
167 


2.27 
2.54 
2.84 


182 
183 
185 


2.77 
3.03 
3.35 


203 3.36 

202 3.60 

203 3.90 


225 
223 
222 


4.07 
4.29 
4.55 


244 
242 
241 


4.84 
5.07 
5.30 


1900 
2000 
2100 


22440 
23620 
24800 


.225 
.250 
.275 


152:2.78 
1573.14 
161 3.52 


170 
173 
177 


3.19 
3.58 
4.03 


187 
190 
193 


3.69 
4.08 
4.51 


205'4.23 
2064.64 
208 5.04 


2224. 87 
2225.25 
223j5.67 


240 5.60 
240 5.92 
240 6.35 


2200 
2300 
2400 


25980 
27160 
28340 


.302 
.330 
.360 


166 3.93 
17l|4.41 
176|4.90 


181 
186 
190 


4.47 
4.97 
5.50 


197 
200 
203 


4.96 
5.48 
6.02 


211 
215 
217 


5.47 
6.00 
6.56 


2266.10 
228 6.61 
230|7.18 


241 6.83 
2427.27 
244 7.82 


2500 
2600 
2800. 


29520 
30710 
33070 


.390 
.422 
.489 


181 
187 
197 


5.41 
6.02 

7.28 


195 
199 

208 


6.01 
6.66 
7.98 


208 
211 
220 


6.66 
7.25 
8.67 


220 
224 
231 


7.15 
7.88 
9.30 


233 
237 
243 


7.76 
8.42 
9.88 


247 8.43 
249 9.15 
256 10.5 


3000 
3200 
3400 


35430 
37790 
40150 


.560 
.638 
.721 


208 


8.91 


219 


9.40 


229 
239 


10.3 
12.0 


240 
249 


10.9 
12.8 


251 11.6 
260 13.5 
269,15.7 


260 12.2 
270 14.3 
278jl6.5 



Outlet 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1"S. P. 


1K"S.P. 


ly/' S. P. 


l^i"S.P. 


2" S. P. 


2H"S.P. 


velocity, 
ft. per 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


a 
P4 


ft 


ft 


ft 


ft 


ft 


ft 


w" 


ft 


w" 


ft 

P3 


ft 


1300 
1400 
1500 


15360 
16530 
17720 


.106 
.122 
.141 


273 
270 
267 


5.18 
5.34 
5.53 


307 
304 


7.15 
7.29 


342 
339 


8.99 
9.31 


370 


11.3 










1600 
1700 
1800 


18900 
20080 
21250 


.160 
.180 
.202 


264 
261 
259 


5.71 
5.90 
6.15 


301 
298 
294 


7.57 
7.73 
8.01 


336 
332 
328 


9.56 
9.80 
10.0 


367 
362 
359 


11.6 
11.8 
12.2 


397 
392 
389 


13.8 
14.2 
14.5 


448 
443 


19.1 
19.4 


1900 
2000 
2100 


22440 
23620 
24800 


.225 
.250 
.275 


258 
257 
257 


6.41 
6.74 
7.10 


292 
291 
289 


8.26 
8.59 
8.91 


326 
323 
320 


10.3 
10.5 
10.9 


356 
352 
350 


12.5 
12.8 
13.1 


386 
381 
378 


14.8 
15.2 
15.6 


439 19.8 
435 20.2 
432|20.6 


2200 
2300 
2400 


25980 
27160 
28340 


.302 
.330 
.360 


256 
257 

258 


7.54 
8.04 
8.59 


288 
287 
287 


9.23 
9.72 
10.1 


318 
317 
316 


11.3 
11.7 
12.2 


347 
344 
342 


13.4 
13.7 
14.3 


376 15.9 
373 16.3 
369 16.7 


429 21.0 
42321.4 
421,21.9 


2500 
2600 
2800 


29520 
30710 
33070 


.390 
.422 
.489 


259 
261 
267 


9.23 
9.80 
11.3 


287 
288 
290 


10.8 
11.3 
12.9 


314 
313 
314 


12.6 
13.2 
14.7 


341 
340 
338 


14.8 
15.3 
16.5 


368 17.2 
366 17.7 
363 18.9 


418 22.4 
41622.8 
411 24.0 


3000 
3200 
3400 


35430 
37790 
40150 


.560 
.638 
.721 


273 
279 

288 


13.0 
14.8 
17.1 


294 
300 
307 


14.5 
16.4 
18.6 


317 16.3 
320 18.1 
327 20.3 


340 
341 
344 


18.2 
20.1 
22.2 


362 20.3 

363 22.2 

364 24.2 


409 25.4 
40627.0 
405 28.8 


3600 
3800 
4000 


42510 
44880 
47240 


.810 

.900 

1.000 


294 


19.6 


314 


21.1 


332 22.8 
339 25.5 


350 
356 
362 


24.8 
27.4 
30.5 


369 26.7 
372 29.5 
378 32.4 


407 31.3 
409 33.9 
411,36.9 



APPENDIX 



297 



Table XXIV. — No. 10 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


K" S. P. 


M"S.P. 


K" S. P. 


^"S.P. 


^" S. P. 


%" S. P. 


a 




a 




a 1 


a 




a 




a 




mm. 


per mm. 


press. 


a 


& 


P5 


a 


a 


^ 


a 


a 


a 


a 


a 
f4 


a 


1000 
1100 
1200 


14580 
16040 
17500 


.063 
.076 
.090 


116 
115 
116 


1.04 
1.16 
1.32 


145 
143 
143 


1.63 
1.74 
1.87 


167 


2.58 














1300 
1400 
1500 


18960 
20410 
21870 


.106 
.122 
.141 


118 
120 
123 


1.50 
1.73 
1.99 


141 
142 
143 


2.04 
2.25 
2.52 


165 
164 
163 


2.73 
2.92 
3.13 


187 
185 
184 


3.52 
3.69 
3.90 


206 
204 


4.61 

4.78 


223 


5.77 


1600 
1700 
1800 


23330 
24790 
26240 


.160 
.180 
.202 


126 
129 
133 


2.29 
2.64 
3.03 


144 
147 
150 


2.80 
3.14 
3.51 


164 
165 
166 


3.42 
3.74 
4.13 


183 
182 
183 


4.15 
4.45 
4.81 


202 
201 
200 


5.02 
5.30 
5.61 


220 
218 
217 


5.97 
6.26 
6.55 


1900 
2000 
2100 


27700 
29160 
30620 


.225 
.250 
.275 


137 
141 
145 


3.43 
3.88 
4.35 


153 
156 
159 


3.94 
4.42 
4.97 


168 
171 
174 


4.55 
5.04 
5.56 


184 
185 
187 


5.22 
5.72 
6.22 


200 
200 
201 


6.01 
6.48 
7.00 


216 
216 
216 


6.91 
7.31 

7.84 


2200 
2300 
2400 


32080 
33540 
34990 


.302 
.330 
.360 


149 
154 
158 


4.85 
5.44 
6.05 


163 
167 
171 


5.51 
6.14 
6.79 


177 
180 
183 


6.12 
6.76 
7.43 


190 
193 
195 


6.76 
7.40 
8.10 


203 
205 
207 


7.54 
8.16 
8.86 


217 
218 
220 


8.43 
8.98 
9.65 


2500 
2600 
2800 


36450 
37910 
40830 


.390 
.422 
.489 


163 

168 
177 


6.68 
7.43 
8.99 


175 
179 
187 


7.42 
8.22 
9.85 


187 
190 
198 


8.22 
8.95 
10.7 


198 
202 
208 


8.83 
9.73 
11.5 


210 
213 
219 


9.58 
10.4 
12.2 


222 
224 
230 


10.4 
11.3 
13.0 


3000 
3200 
3400 


43740 
46660 
49570 


.560 
.638 
.721 


187 


11.0 


197 


11.6 


206 
215 


12.7 
14.8 


216 

224 


13.5 
15.8 


226 
234 
242 


14.3 
16.7 
19.4 


234 
243 
250 


15.1 
17.6 
20.4 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 
for 
total 


1"S.P. 


13^i"S.P. 


iVi" S. P. 


IK" S. P. 


2" S. P. 


2K" S. P. 


a 




a 




a 




a 




a 




a 




mm. 


per mm. 


press. 


a 
p4 


a 


a 
P^ 


a 


«• 


a 


a 


a 


a 


a 


a 


a 


1300 
1400 
1500 


18960 
20410 
21870 


.106 
.122 
.141 


246 
243 
240 


6.40 
6.59 
6.83 


276 

274 


8.83 
9.00 


308 
305 


11.1 
11.5 


333 


13.9 










1600 
1700 
1800 


23330 
24790 
26240 


.160 
.180 
.202 


238 
235 
233 


7.05 
7.28 
7.59 


271 
268 
265 


9.34 
9.54 
9.89 


302 
299 
295 


11.8 
12.1 
12.4 


330 
326 
323 


14.3 
14.6 
15.0 


357 
353 
350 


17.0 
17.5 
17.9 


403 
399 


23.6 
24.0 


1900 
2000 
2100 


27700 
29160 
30620 


.225 
.250 
.275 


232 
231 
231 


7.91 
8.32 
8.77 


263 
262 
260 


10.2 
10.6 
11.0 


293 
291 

288 


12.7 
13.0 
13.5 


320 
317 
315 


15.4 
15.8 
16.2 


347 
343 
340 


18.3 
18.7 
19.2 


395 
391 
389 


24.4 
24.9 
25.4 


2200 
2300 
2400 


32080 
33540 
34990 


.302 
.330 
.360 


230 
231 
232 


9.31 
9.92 
10.6 


259 

258 
258 


11.4 
12.0 
12.5 


286' 13.9 
285 14.4 
284 15.0 


312 
310 
308 


16.6 
17.1 
17.7 


338 
336 
332 


19.6 
20.1 
20.6 


386 
381 
379 


25.9 
26.4 
27.0 


2500 
2600 
2800 


36450 
37910 
40830 


.390 
.422 
.489 


233 
235 
240 


11.4 
12.1 
13.9 


258 13.3 

259 14.0 
261 15.9 


283 15.6 
282 16.3 
283,18.1 


307 
306 
304 


18.2 
18.9 
20.4 


331 
329 
327 


21.2 
21.8 
23.3 


376 
374 
370 


27.6 
28.2 
29.6 


3000 
3200 
3400 


43740 
46660 
49570 


.560 
.638 
.721 


246 
251 
259 


16.0 
18.3 
21.1 


265 
270 

276 


17.9 
20.3 
22.9 


285 20.1 

288 22.4 
294 25.1 


306 22.4 

307 24.8 
31027.4 


326 
327 

328 


25.0 
27.4 
29.9 


368 
365 
364 


31.3 
33.3 
35.6 


3600 
3800 
4000 


52490 
55400 
58320 


.810 

.900 

1.000 


265 


24.2 


283 


26.0 


299 
305 


28.1 
31.5 


315 
320 
326 


30.6 
33.8 
37.6 


332 
335 
340 


32.9 
36.4 
40.0 


366 
368 
370 


38.6 
41.8 
45.6 



298 



HEATING AND VENTILATION 



Table XXV. — No. 11 Niagara Conoid al Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


H" S. P. 


H" S. P. 


3^2" S. P. 


^^"S.P. 


H" S. P. 


>^"S.P. 


a 




a 




B 




B 




B 




B 




mm. 


per min. 


press. 


0. 




ft 

pi 


ft 


ft 

pi 


S 


ft 


ft 


ft 

p4 


ft 


ft 


ft 


1000 
1100 
1200 


17640 
19410 
21170 


.063 
.076 
.090 


106 
105 
106 


1.26 
1.40 
1.60 


132 
130 
130 


1.97 
2.11 
2.26 


152 


3.12 














1300 
1400 
1500 


22930 
24700 
26460 


.106 
.122 
.141 


107 
109 
112 


1.82 
2.09 
2.41 


128 
129 
130 


2.47 
2.72 
3.05 


150 3.30 
149 3.53 
148 3.79 


170 
168 
167 


4.26 
4.47 
4.72 


187 
186 


5.58 

5.78 


203 


6.98 


1600 
1700 
1800 


28230 
29990 
31750 


.160 
.180 
.202 


115 
117 
121 


2.77 
3.20 
3.67 


131 
134 
136 


3.39 
3.80 
4.25 


149 4.14 
1504.53 
151 5.00 


166 
166 
166 


5.02 
5.39 
5.82 


184 6.08 
183 6.41 
182 6.79 


200 7.22 
198 7.58 
197 7.93 


1900 
2000 
2100 


33520 
35280 
37050 


.225 
.250 
.275 


125 
128 
132 


4.15 
4.70 
5.26 


139 
142 
145 


4.77 
5.35 
6.01 


153 
156 
158 


5.51 
6.10 
6.73 


167 6.32 
1686.92 
170 7.53 


1827.27 
1827.84 
1838.87 


196 8.36 
19618.85 
1969.49 


2200 
2300 
2400 


38810 
40580 
42340 


.302 
.330 
.360 


136 
140 
144 


5.87 
6.58 
7.32 


148 
152 
156 


6.67 
7.43 

8.22 


161 
164 
166 


7.41 
8.18 
8.99 


173 8.18 
1768.95 
177 9.80 


185 
186 
188 


9.12 
9.87 
10.7 


197 10.2 

198 10.9 
200 11.7 


2500 
2600 ' 
2800 


44100 
45870 
49400 


.390 
.422 
.489 


148 
153 
161 


8.08 
8.99 
10.9 


159 
163 
170 


8.98 
9.95 
11.9 


170 
173 
180 


9.95 
10.8 
13.0 


180 10.7 
184;il.8 
189 13.9 


191 
194 
199 


11.6 
12.6 

14.8 


202 12.6 
204113.7 
209 15.7 


3000 
3200 
3400 


52910 
56450 
59980 


.560 
.638 
.721 


170 


13.3 


179 


14.0 


187 
196 


15.4 
17.9 


196|l6.3 
204 19.1 


206 
213 
220 


17.3 
20.2 
23.5 


213 
221 
227 


18.3 
21.3 

24.7 



Outlet 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1" S. P. 


1K"S.P. 


13^" S. P. 


1K"S.P. 


2" S. P. 


2M" S. P. 


velocity, 
ft. per 


B 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


ft 


ft 

w 


ft 


ft 


ft 


a 


ft 

f4 


ft 


ft 

pi 


ft 


ft 

pi 


S 


1300 
1400 
1500 


22930 
24700 
26460 


.106 
.122 
.141 


224 
221 
218 


7^74 
7.97 
8.26 


251 
249 


10.7 
10.9 


1 

28o'l3.4 
277J13.9 


303 


16.8 










1600 
1700 
1800 


28230 
29990 
31750 


.160 
.180 
.202 


216 
214 
212 


8.53 
8.81 
9.18 


246 11.3 
244 11.6 
241 12.0 


275 
272 
268 


14.3 
14.7 
15.0 


300 
296 
294 


17.3 

17.7 
18.2 


325 '20. 6 
321 21.2 
318^21.7 


366 
363 


28.6 
29.0 


1900 
2000 
2100 


33520 
35280 
37050 


.225 
.250 
.275 


211 
210 
210 


9.57 
10.1 
10.6 


239 
238 
236 


12.4 
12.8 
13.3 


266 
265 
262 


15.4 
15.7 
16.3 


291 

288 
286 


18.6 
19.1 
19.6 


31622.2 
312122.6 
309 23.2 


359 
356 
354 


29.5 
30.1 
30.7 


2200 
2300 
2400 


38810 
40580 
42340 


.302 
.330 
.360 


209 
210 
211 


11.3 
12.0 
12.8 


236 
235 
235 


13.8 
14.5 
15.1 


260 
259 
258 


16.8 
17.4 
18.2 


284 
282 
280 


20.1 
20.7 
21.4 


307 23.7 
306 24.3 
30224.9 


351 
346 
345 


31.3 
32.0 
32.7 


2500 
2600 
2800 


44100 
45870 
49400 


.390 
.422 
.489 


212 
214 
218 


13.8 
14.6 
16.8 


235 
236 
237 


16.1 
17.0 
19.2 


257 
256 
257 


18.9 
19.7 
21.9 


279 
278 
276 


22.0 
22.9 
24.7 


301 
299 
297 


25.7 
26.4 
28.2 


342 
340 
336 


33.4 
34.1 
35.8 


3000 
3200 
3400 


52910 
56450 
59980 


.560 
.638 
.721 


224 
228 
236 


19.4 
22.1 
25.5 


241 
246 
251 


21.7 
24.6 
27.7 


259 
262 
267 


24.3 
27.1 
30.4 


278 
279 
282 


27.1 
30.0 
33.2 


296 
297 

248 


30.3 
33.2 
36.2 


335 
332 
331 


37.9 
40.3 
43.1 


3600 
3800 
4000 


63510 
67030 
70560 


.810 

.900 

1.000 


241 


29.3 


257 


31.5 


272 

277 


34.0 
38.1 


286 
291 
296 


37.0 
40.9 
45.5 


302 
305 
309 


39.8 
44.1 
48.4 


333 
335 
336 


46.7 
50.6 
55.2 



APPENDIX 



299 



Table XXVI. — No. 12 Niagara Conoidal Fan (Type N) Capacities and 
Static Pressures at 70°F. and 29.92 Inches Barometer 



Outlet 
velocity, 
ft. per 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


Vi" S. P. 


H" S. P. 


H"S.P. 


M"S.P. 


K" S. P. 


K"S. P. 


a 




a 




a 




a 




a 




a 




min. 


per min. 


press. 


a 




a 


ft 


a 
pi 


£ 


a 


a 


a 


a 


a 


a 
W 


1000 
1100 
1200 


21000 
23090 
25190 


.063 
.076 
.090 


97 
96 
97 


1.50 
1.67 
1.90 


1212.35 
1192.51 
1192.69 


139 


3.72 














1300 
1400 
1500 


27290 
29390 
31490 


.106 
.122 
.141 


98I2.I6 
100 2.49 
103 2.87 


1182.94 
118 3.24 
1193.63 


138 
137 
136 


3.93 
4.21 
4.51 


156 5.07 
154 5.31 
153 5.62 


172 6.64 
170 6.88 


186 8.31 


1600 
1700 
1800 


33600 
35690 
37790 


.160 
.180 
.202 


105 3.30 
108 3 . 80 
1114.36 


120 4.03 
123 4.52 
125 5.06 


137'4.93 
138 5.39 
138 5.95 


153 5.98 

152 6.41 

153 6.93 


168 7.23 
168 7.63 
1678.08 


183 8.60 
182 9.02 
181 9.43 


1900 
2000 
2100 


39890 
41990 
44090 


.225 
.250 
.275 


114 4.94 
118 5.59 
121 6.27 


1285.67 
130 6.37 

133.7.16 

1 


140 6.55 
143 7.26 
145 8.01 


1537.52 
1548.24 
156 8.96 


167 8.66 

167 9.33 

168 10.1 


1809.95 
180 10.5 
18011.3 


2200 
2300 
2400 


46190 
48290 
50390 


.302 
.330 
.360 


124 6.99 
128 7.83 
1328.71 


136 7.94 
139 8.84 
143 9.78 


148 8.81 
150 9.74 
153 10.7 


158 9.74 
161 10.7 
163 11.7 


169 10.9 
171 11.8 
173 12.8 


181 12.2 
18212. 9 
183 13.9 


2500 
2600 
2800 


52490 
54590 
58790 


.390 
.422 
.489 


136 9.62 
140 10.7 
148 13.0 


146'l0.7 
149 11.8 
156 14.2 


156 11.8 
158 12.9 
165 15.4 


165 12.7 
168 14.0 
173 16.6 


175 13.8 
178 15.0 
183 17.6 


185^15.0 
187 16.3 
192:18.7 


3000 
3200 
3400 


62980 
67180 
71380 


.560 
.638 
.721 


156 15.9 


164 


16.7 


172 18.3 
179 21.3 


180 19.5 

187,22.8 


188 20.6 
195 24.1 
202j27.9 


19521.8 
203|25.4 
208 29.4 



Outlet 


Capacity, 

cu. ft. 

air 


Add 

for 

total 


1" S. P. 


1M"S. P. 


1J^"S. P. 


1M"S. P. 


2" S. P. 


2K" S. P. 


velocity, 
ft. per 


a 




a 




a 




a 




a 




a 




mm. 


per min. 


press. 


a 
P5 


a 

W 


«• 


a 

W 


a 

p4 


a 


a 

pi 


a 


a 
pi 


^ 


a 

pi 


a 

W 


1300 
1400 
1500 


27290 
29390 
31490 


.106 
.122 
.141 


205 9.22 
203 9.49 
200 9.84 


230 

228 


12.7 
13.0 


257 
254 


16.0 
16.6 


278 20.0 










1600 
1700 
1800 


33600 
35690 
37790 


.160 
.180 
.202 


198 10.2 
196 10.5 
194 10.9 


226 
223 
221 


13.5 
13.7 
14.3 


252 17.0 
249 17.4 
246 17.9 


27520.6 
272 21.0 
269 21.6 


298 
294 
292 


24.5 
25.2 
25.8 


336 
333 


34.0 
34.6 


1900 
2000 
2100 


39890 
41990 
44090 


.225 
.250 
.275 


193 11.4 
193 12.0 
193 12.6 


219 
218 
217 


14.7 
15.3 
15.8 


244 18.3 
243 18.7 
240 19.5 


267 22.2 
264 22.8 
263 23.3 


289|26.4 
286 26.9 
283 27.7 


329 35.1 
326 35.9 
32436.6 


2200 
2300 
2400 


46190 
48290 
50390 


.302 
.330 
.360 


192 13.4 

193 14.3 
193 15.3 


216 
215 
215 


16.4 
17.3 
18.0 


238 20.0 
238 20.7 
237 21.6 


260 23.9 
258 24.6 
257 25.5 


282 28.2 
280 29.0 
277 29.7 


322 37.3 
31838.0 
316138.9 


2500 
2600 
2800 


52490 
54590 
58790 


.390 
.422 
.489 


194 16.4 
196 17.4 
200 20.0 


215 
216 
218 


19.2 
20.2 
22.9 


236 22.5 
23523.5 
23626.1 


256 26.2 
255 27.2 
253 29.4 


27630.5 
27431.4 
273 33.6 


313139.8 
31240.6 
308,42.6 


3000 
3200 
3400 


62980 
67180 
71380 


.560 
.638 
.721 


205 23.0 
209 26.4 
216 30.4 


221 25.8 
225 29.2 
230 33.0 


238 29.0 
240 32.3 
245 36.2 


255 32.3 

256 35.7 
258 39.5 


272 36.0 

273 39.5 
273 43.1 


307 45.1 
304 48.0 
303 51.3 


3600 
3800 
4000 


75580 
79780 
83980 


.810 

.900 

1.000 


221 


34.9 


236 


37.5 


249 40.5 
254 45.4 


263^44.1 
267,48.7 
272:54.2 


27747.4 
279 52.4 
283 57.6 


305 55.6 
307:60.2 
308 65.7 



INDEX 



Absolute temperature 4 

zero 4 

Adiabatic saturation 172 

Air and its properties 169-178 

Air, composition of 169, 180 

conditioning 175, 244-251 

cooling 176,186,249-251 

distribution 184, 189 

-ducts 214-222 

flow of, in ducts 209-216 

friction of, in ducts. . . 214^216 

infiltration of 12,17 

measurement of 210-214 

motion 179,184,187 

pollution 179 

properties of 176, 177 

psychrometric chart for 

174, 175, 273-275 

specific heat of 177 

supply 179,181 

measurement of .... 182-183 

total heat of 172 

-valves Ill 

venting 123 

-washers 217, 244-251 

Air-line system 92 

valves 92, 112 

Allen's rule for heat loss 22 

Anemometer 213 

Anthracite coal 69 

Argon 169 

Ash 69,73 

Atmospheric system 96 

Automatic temperature control 

163-168 

Back pressure valve 141 

Bacteria 179 

Bituminous coal 69, 73 

Body, heat loss from the 

179, 185, 186 

Boiler connections 130 

horsepower 81 

301 



Boilers 69-86 

cast-iron 75 

downdraft 77 

firebox 76 

magazine feed 80 

marine type 77 

proportions of 80 

rating of 81 

requirements of . .' 74 

return tubular 76 

round 75 

sectional 75 

selection of 259 

smokeless 79 

steel 75 

types of 74-80 

water tube 77 

Boot 198 

Branches 121 

British thermal unit 4 

Calorific value of coal 71 

Carbon dioxide, 72, 169, 170, 

180, 182-183 

monoxide 72, 180 

Carbonic acid gas. See Carbon 

dioxide. 
Carpenter's rule for heat loss ... 22 

Centigrade scale 2 

Central heating 258-268 

Centrifugal fan. See Fans. 

Check valve 107, 108 

Chimneys 83-86 

Clinkers 73 

CO 2. See Carbon dioxide. 

Coal 69-74 

analysis of 70 

composition of 70 

consumption of 255-257 

sizes of 70 

Coefficients of heat transmission 

through walls . . 17, 269-272 
from radiators 53 



302 



INDEX 



Coke 71 

Cold-air pipe 196 

Combustion 71-73, 78 

Comfort zone 185 

Condensation, drainage of, 119, 120 

in underground steam lines, 264 

Conduction 9-10 

Conduit, for pipes 262-263 

Contractor's guarantee 58 

Convection 11 

factor 13, 14 

Cost of heating 255-257 

Dalton's law of gases 171 

Damper 253 

regulator 83 

De-humidification 249-251 

Dewpoint 171,174 

Diaphragm expansion joint. .. . 265 

motor 167 

valve. 166 

Dirt pocket 127 

Disc fan 233 

Distribution systems 260-262 

Downdraf t furnace 78 

Draft 83-86 

Drip connections 123, 127 

Dry return system 90 

Dust 179,188 

Dynamic head 209 

Economy of heating systems. . . 31 

Ejector. 92 

Equivalent evaporation 81 

Estimating of heating require- 
ments 255-257 

Expansion fittings 264 

of pipes 119, 264 

tank 147, 148 

Exposure, factors for 21 

Factory heating 253-255 

Fahrenheit scale 2 

Fan heaters 233-242 

systems 30 

arrangement of 207 

design of 206-243 

types of 206,252-256 



Fans, centrifugal, blades and 

housings 224-225 

efficiency of 226 

laws of 226 

power required by 225 

straight blade 226 

theory of 223 

Fittings, flanged 105 

resistance of 136, 154 

screwed 104 

Flanges 105 

Flow of air. See Air. 

Flue gases 72 

radiators 67 

Flues 84 

foul-air 202 

hot-air 197 

Forced circulation hot-water 

heating 158-162 

Friction, of air in pipes 214-216 

of fluids in pipes 131 

in hot v/ater systems, 144- 

146, 152-154, 15^162 

Fuels 69-74 

Furnace, boiler 77-79 

heating 191-205 

hot-air 26, 191, 192-195 

pipeless 203 

test of 204 

Gage 83 

Gaskets 106 

Gate valve 107 

Generator 157-158 

Glass, heat transmission of . . 17, 272 

Globe valve 107 

Grate surface 81, 195 

Grates 25,77 

Gravity hot-water heating 142 

indirect radiators. See 
Radiators. 

system of distribution 260 

Guarantee, checking of 58 

Heat 1-8 

definition of 1 

flow of 1 

given off by persons 23 

latent 35, 37 



INDEX 



303 



Heat, loss of, from a body 9 

from buildings. . 179, 185-186 

Allen's rule 22 

approximate rules .... 21 

calculation of 20 

Carpenter's rule 22 

coefficients of. . 16, 269-272 
from underground pipes. 264 

measurement of 1 

of superheat 34, 37, 172 

of the liquid 34,35,37,172 

of vaporization 34, 37, 172 

total 36 

transmission from radiators 

51-55, 63 

value of coal 71 

Heaters for fan systems. . . .233-242 

.friction in 238-241 

installation of 241 

[pipe coil 235 

vento 234 

hot-water 86 

Heating, central 258-268 

different methods of 25-32 

direct 25,27 

fan systems of 30 

furnace 191-205 

hot water 28, 142-162, 261 

indirect 25 

of auditoriums 255 

of factories 253 

of schools 252 

of theatres 255 

steam required for 257 

surface of boilers 81 

systems, economy of 31 

hot-water 142-162 

losses in 31 

steam 87-101 

Horsepower, boiler 81 

Hot-air furnace heating. . . .191-205 

pipes 197, 199-201 

Hot-water heaters 86 

systems 142-162, 261 

Humidification 195 

See also Air conditioning. 

Humidifier 196 

Humidifying' efficiency 250 

Humidity, absolute 172 



Humidity, control of 248 

measurement of 173 

relative 172 

standards of 179, 184 

See also Air conditioning. 

Infiltration 12,17 

Intermittent heating 21 

Joule's equivalent 8 

k, values of 16, 269-272 

Lamps, pollution from 180 

Leaders 197-201 

Magazine-feed boiler 80 

Mains, steam 87, 121 

Mercury seal generator 158 

Mixing damper 253 

Mixtures of substances 38-44 

Moisture, in fuel 71 

in air. See Water vapor 
and Humidity. 

Neon 169 

Nitrogen 169 

Odors 179,180,187 

One-pipe systems. See Single- 
pipe systems. 
Overhead system, steam... 91, 118 

water 148,149 

Oxygen 169, 179, 180 

Ozone 164, 188 

Painting of radiators 52 

Partial pressures, law of.' 171 

Perspiration 184 

Petterson and Palmquist appa- 
ratus 170 

Pipe 102 

coil heaters. See Heaters. 

coils 51, 130 

covering 109-111 

dimensions of 103 

fittings 104, 105 

flanges 105 

hangers 124-125 



304 



INDEX 



Pipe, threads 104 

unions 105 

Pipes, hot-air 197-201 

size of, for steam 

133-137, 267-268 

water 151-157,159-162 

Piping, for hot water systems. . 157 

steam 117-141 

underground 262-266 

Pitottube 211-213 

Power plants 139-140, 258 

Pressure drop in steam pipes 

131-136 

gage 83 

Proximate analysis of coal 71 

Psychrometer. 174 

Psychrometric chart, 174, 175, 

273-275 

Pumpage 159 

Pump-return system 260 

Pumps,, circulating 162 

vacuum 99 

Radiation, approximate rules 

for 58, 66 

proportioning of 57, 58, 65 

transmission of heat by . . . 9 

Radiators 45-68 

cast-iron 45-49 

classification of 45 

connections to 128-129, 137-138 

direct 45 

effect of enclosing 57 

of painting 52 

flue 67 

heating surface of 48, 50 

heat transmission from. . 51-55 

indirect 45,60-67 

location of 56 

pipe 51 

pressed metal 49, 55 

semi-indirect 45 

tappings 49 

wall type 48 

Re-circulating duct 196 

Reducing valve 115, 141 

Registers 198,202 

Regulation of temperature . 1 63-1 68 
Relief system 88, 122 



Respiration 169, 180 

Retarder 96 

Return piping 126 

Reversed return 147 

Riser vent 112 

Risers 87,122,127 

hot-air 197-201 

Safety valve 82 

Saturated steam 33-34 

Saturation, adiabatic 172 

School buildings 252-253 

Semi-anthracite coal 69 

-bituminous coal 69, 73 

-indirect radiators 67 

Separator 115 

Single-duct system 219, 252 

-pipe systems, steam 

87-89, 117 

water 149,151 

Size of pipes 119, 133 

Sling psychrometer 174 

Slip joint 264 

Smoke 12 

Smokeless combustion 73, 78 

furnaces 77, 79 

Specific heat, definition 5 

of substances 6 

of water 272 

Stacks 82-86 

Static efficiency 226 

head 209 

Steam boilers. See Boilers. 

consumption of 257 

flow of, in pipes 131-136 

formation of 33 

heating 27 

-heating systems 87-101 

piping 117-141 

properties of 33-44 

table 37 

saturated 33, 34 

superheated 33 

Stefan's law 10 

Stoves 26 

Sulphur 73 

Tapping of radiators. . 49 

Temperature, absolute 4 



INDEX 



305 



Temperature, colors 4 

control of 163-168 

definition of 1 

inside 17 

measurement of 2-3 

standards of 179, 184-185 

Theatres, heating of 255 

Thermodynamics, first law of . . 8 

Thermometer 2-3 

wet- and dry-bulb 173 

Thermostatic control 163-168 

Tile conduit 264 

Total efficiency 226 

head 209 

Traps, bucket 112, 114 

float 95,112,113 

radiator 94,95,127 

thermostatic 94, 127 

tilting 114 

Trunk line duct system 221 

Tunnels 266-268 

Two-pipe systems, steam . . 87, 89-91 
water 147,148 

Ultimate analysis of coal 71 

Underground piping 262-266 

Unions 105 

Unit of heat , 4 

Unwin's coefficient 132 

Vacuum pump 99 

system, 92, 99-101, 108, 

126, 163 

Valves, air- Ill 

air-line 112 

back-pressure 141 

check 107 

gate 107 

globe 107 

location of 127 



Valves, radiator 97, 108 

reducing 115, 141 

Vapor system, 93, 98, 99, 108, 

126, 163 
water. See Water vapor. 

Velocity head 209 

Ventilation 31, 179-190 

heat required for 19, 31 

methods of 189 

of auditoriums 255 

of schools 252 

of theatres 255 

standards of 179 

systems of 30 

See also Fan systems. 

Vento heaters. See Heaters. 

Volatile matter 69, 72, 73 

Walls, coefficients of heat trans- 
mission through, 17, 

269-272 
flow of heat through. ... 12-17 

Water column 82 

pan 195 

specific heat of 272 

thermal properties of 272 

vapor 169, 170-178, 180 

See also Humidity. 
Wet- and dry-bulb thermo- 
meter 173 

-bulb temperature. . . . 173, 175 

-return system 90 

Windows, air leakage through. . 19 
heat loss through. . 17, 269-272 
Wolpert method of CO 2 deter- 
mination 170 

Wood casing 262 



Zero, absolute. 



20 



